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Sample records for ag-pd bimetallic nanostructures

  1. Melting phenomena: effect of composition for 55-atom Ag-Pd bimetallic clusters.

    PubMed

    Cheng, Daojian; Wang, Wenchuan; Huang, Shiping

    2008-05-14

    Understanding the composition effect on the melting processes of bimetallic clusters is important for their applications. Here, we report the relationship between the melting point and the metal composition for the 55-atom icosahedral Ag-Pd bimetallic clusters by canonical Monte Carlo simulations, using the second-moment approximation of the tight-binding potentials (TB-SMA) for the metal-metal interactions. Abnormal melting phenomena for the systems of interest are found. Our simulation results reveal that the dependence of the melting point on the composition is not a monotonic change, but experiences three different stages. The melting temperatures of the Ag-Pd bimetallic clusters increase monotonically with the concentration of the Ag atoms first. Then, they reach a plateau presenting almost a constant value. Finally, they decrease sharply at a specific composition. The main reason for this change can be explained in terms of the relative stability of the Ag-Pd bimetallic clusters at different compositions. The results suggest that the more stable the cluster, the higher the melting point for the 55-atom icosahedral Ag-Pd bimetallic clusters at different compositions.

  2. Study of Ag-Pd bimetallic nanoparticles modified glassy carbon electrode for detection of L-cysteine

    NASA Astrophysics Data System (ADS)

    Murugavelu, M.; Karthikeyan, B.

    2014-11-01

    Ag-Pd bimetallic nanoparticles (Ag-Pd BNPs) as an enhanced sensing material with improved electronic transmission rates in the electrochemical sensing of L-cysteine (L-cys) has been reported. The morphology of Ag-Pd BNPs was characterized with X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and cyclic voltammetry (CV). Oxidation of L-cys on Ag-Pd BNPs is investigated in detail by discussing the effect of the structure and from the electrocatalytic oxidation of L-cys. We found that the Ag-Pd BNPs exhibited high electrocatalytic activity towards L-cys oxidation in neutral condition and could be used for the development of nonenzymatic L-cys sensor. Based on the efficient catalytic ability of Ag-Pd BNPs, the fabricated biosensor exhibited a wide linear range of responses to the L-cys with the concentration detection limit of nearly down to 2 mM with fast response time.

  3. Controllable galvanic synthesis of triangular Ag-Pd alloy nanoframes for efficient electrocatalytic methanol oxidation.

    PubMed

    Xu, Lin; Luo, Zhimin; Fan, Zhanxi; Yu, Sijia; Chen, Junze; Liao, Yusen; Xue, Can

    2015-06-01

    Triangular Ag-Pd alloy nanoframes were successfully synthesized through galvanic replacement by using Ag nanoprisms as sacrificial templates. The ridge thickness of the Ag-Pd alloy nanoframes could be readily tuned by adjusting the amount of the Pd source during the reaction. These obtained triangular Ag-Pd alloy nanoframes exhibit superior electrocatalytic activity for the methanol oxidation reaction as compared with the commercial Pd/C catalyst due to the alloyed Ag-Pd composition as well as the hollow-framed structures. This work would be highly impactful in the rational design of future bimetallic alloy nanostructures with high catalytic activity for fuel cell systems.

  4. EXAFS Studies of Bimetallic Ag-Pt and Ag-Pd Nanorods

    SciTech Connect

    Lahiri, D.; Chattopadhyay, S.; Bunker, B.A.; Doudna, C.M.; Bertino, M.F.; Blum, F.; Tokuhiro, A.; Terry, J.

    2008-10-30

    Nanoparticles of Ag-Pt and Ag-Pd with high aspect ratios were synthesized using a radiolysis method. Gamma rays at dose rates below 0.5 kGy/h were used for irradiation. The nanoparticles were characterized by transmission electron microscopy (TEM), optical absorption spectroscopy and x-ray Absorption Fine Structure (XAFS) spectroscopy. Bright field micrographs show that Ag-Pt nanowires are composed of large particles with diameters ranging from 20-30 nm and joined by filaments of diameter between 2-5 nm. The Ag-Pd nanowires have diameters of 20-25 nm and lengths of 1.5 {micro}m. For XAFS measurements, the Pt L3 edge (11.564 keV), Ag K-edge (25.514 keV) and Pd K-edge (24.350 keV) were excited to determine the local structure around the respective atoms in the cluster. The Ag-Pt particles were found to possess a distinct core-shell structure with Pt in the core surrounded by Ag shell, with no indication of alloy formation. However, nanorods of Ag-Pd have formed an alloy for all the alloy compositions.

  5. Triangular Ag-Pd alloy nanoprisms: rational synthesis with high-efficiency for electrocatalytic oxygen reduction

    NASA Astrophysics Data System (ADS)

    Xu, Lin; Luo, Zhimin; Fan, Zhanxi; Zhang, Xiao; Tan, Chaoliang; Li, Hai; Zhang, Hua; Xue, Can

    2014-09-01

    We report the generation of triangular Ag-Pd alloy nanoprisms through a rationally designed synthetic strategy based on silver nanoprisms as sacrificial templates. The galvanic replacement between Ag nanoprisms and H2PdCl4 along with co-reduction of Ag+/Pd2+ is responsible for the formation of final prismatic Ag-Pd alloy nanostructures. Significantly, these Ag-Pd alloy nanoprisms exhibited superior electrocatalytic activity for the oxygen reduction reaction (ORR) as compared with the commercial Pd/C catalyst. Such a high catalytic activity is attributed to not only the alloyed Ag-Pd composition but also the dominant {111} facets of the triangular Ag-Pd nanoprisms. This work demonstrates the rational design of bimetallic alloy nanostructures with control of selective crystal facets that are critical to achieve high catalytic activity for fuel cell systems.We report the generation of triangular Ag-Pd alloy nanoprisms through a rationally designed synthetic strategy based on silver nanoprisms as sacrificial templates. The galvanic replacement between Ag nanoprisms and H2PdCl4 along with co-reduction of Ag+/Pd2+ is responsible for the formation of final prismatic Ag-Pd alloy nanostructures. Significantly, these Ag-Pd alloy nanoprisms exhibited superior electrocatalytic activity for the oxygen reduction reaction (ORR) as compared with the commercial Pd/C catalyst. Such a high catalytic activity is attributed to not only the alloyed Ag-Pd composition but also the dominant {111} facets of the triangular Ag-Pd nanoprisms. This work demonstrates the rational design of bimetallic alloy nanostructures with control of selective crystal facets that are critical to achieve high catalytic activity for fuel cell systems. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03600j

  6. Trimetallic nanostructures: the case of AgPd/Pt multiply twinned nanoparticles

    PubMed Central

    Khanal, Subarna; Bhattarai, Nabraj; Velázquez-Salazar, J. Jesús; Bahena, Daniel; Soldano, German; Ponce, Arturo; Mariscal, Marcelo M.; Mejía-Rosales, Sergio; José-Yacamán, Miguel

    2013-01-01

    We report the synthesis, structural characterization, and atomistic simulations of AgPd/Pt trimetallic (TM) nanoparticles. Two types of structure were synthesized using a relatively facile chemical method: multiply twinned core-shell, and hollow particles. The nanoparticles were small in size, with an average diameter of 11 nm and a narrow distribution, and their characterization by aberration corrected scanning transmission electron microscopy allowed us to probe the structure of the particles at atomistic level. In some nanoparticles, the formation of a hollow structure was also observed, that facilitates the alloying of Ag and Pt in the shell region and the segregation of Ag atoms in the surface, affecting the catalytic activity and stability. We also investigated the growth mechanism of the nanoparticles using grand canonical Monte Carlo simulations, and we have found that Pt regions grow at overpotentials on the AgPd nanoalloys, forming 3D islands at the early stages of the deposition process. We found very good agreement between the simulated structures and those observed experimentally. PMID:24165796

  7. Global optimization of bimetallic cluster structures. II. Size-matched Ag-Pd, Ag-Au, and Pd-Pt systems.

    PubMed

    Rossi, Giulia; Ferrando, Riccardo; Rapallo, Arnaldo; Fortunelli, Alessandro; Curley, Benjamin C; Lloyd, Lesley D; Johnston, Roy L

    2005-05-15

    Genetic algorithm global optimization of Ag-Pd, Ag-Au, and Pd-Pt clusters is performed. The 34- and 38-atom clusters are optimized for all compositions. The atom-atom interactions are modeled by a semiempirical potential. All three systems are characterized by a small size mismatch and a weak tendency of the larger atoms to segregate at the surface of the smaller ones. As a result, the global minimum structures exhibit a larger mixing than in Ag-Cu and Ag-Ni clusters. Polyicosahedral structures present generally favorable energetic configurations, even though they are less favorable than in the case of the size-mismatched systems. A comparison between all the systems studied here and in the previous paper (on size-mismatched systems) is presented.

  8. Bimetallic nanostructures. II. Finite temperature and applications

    NASA Astrophysics Data System (ADS)

    Montejano-Carrizales, J. M.; Morán-López, J. L.

    1990-12-01

    A systematic study of ordering and segregation at finite temperatures in bimetallic nanoclusters is presented. Icosahedral and cubo-octahedral clusters, with a total number of atoms, N = 13, 55 and 147, are studied. The equilibrium configuration is obtained by calculating the free energy within the regular solution model. The theory is applied to CuPd, NiPt and CuNi nanoclusters. We present results for the temperature dependence of the concentrations at the different shells around the central atom. In most of the cases a strong segregation is found.

  9. Ordered macroporous bimetallic nanostructures: design, characterization, and applications.

    PubMed

    Lu, Lehui; Eychmüller, Alexander

    2008-02-01

    Ordered porous metal nanomaterials have current and future potential applications, for example, as catalysts, as photonic crystals, as sensors, as porous electrodes, as substrates for surface-enhanced Raman scattering (SERS), in separation technology, and in other emerging nanotechnologies. Methods for creating such materials are commonly characterized as "templating", a technique that involves first the creation of a sacrificial template with a specific porous structure, followed by the filling of these pores with desired metal materials and finally the removal of the starting template, leaving behind a metal replica of the original template. From the viewpoint of practical applications, ordered metal nanostructures with hierarchical porosity, namely, macropores in combination with micropores or mesopores, are of particular interest because macropores allow large guest molecules to access and an efficient mass transport through the porous structures is enabled while the micropores or mesopores enhance the selectivity and the surface area of the metal nanostructures. For this objective, colloidal crystals (or artificial opals) consisting of three-dimensional (3D) long-range ordered arrays of silica or polymer microspheres are ideal starting templates. However, with respect to the colloidal crystal templating strategies for production of ordered porous metal nanostructures, there are two challenging questions for materials scientists: (1) how to uniformly and controllably fill the interstitial space of the colloidal crystal templates and (2) how to generate ordered composite metal nanostructures with hierarchical porosity. This Account reports on recent work in the development and applications of ordered macroporous bimetallic nanostructures in our laboratories. A series of strategies have been explored to address the challenges in colloidal crystal template techniques. By rationally tailoring experimental parameters, we could readily and selectively design

  10. Preparation of Ag/Au bimetallic nanostructures and their application in surface-enhanced fluorescence.

    PubMed

    Dong, Jun; Ye, Yanyan; Zhang, Wenhui; Ren, Zebin; Huo, Yiping; Zheng, Hairong

    2015-11-01

    An effective substrate for surface-enhanced fluorescence, which consists of cluster Ag/Au bimetallic nanostructures on a copper surface, was synthesized via a multi-stage galvanic replacement reaction of a Ag cluster in a chlorauric acid (HAuCl4) solution at room temperature. The fabricated silver/gold bimetallic cluster were found to yield large surface-enhanced fluorescence (SEF) enhancement factors for rhodamine 6G probe molecules deposited on the substrate, and also the fluorescence efficiency is critically dependent on the period of nanostructure growth. With the help of proper control reaction conditions, such as the reaction time, and concentration of reaction solutions, the maximum fluorescence enhanced effect was obtained. Therefore, the bimetallic nanostructure substrate also can be adapted to studies in SEF, which will expand the application of SEF.

  11. An inorganic capping strategy for the seeded growth of versatile bimetallic nanostructures

    SciTech Connect

    Pei, Yuchen; Maligal-Ganesh, Raghu V.; Xiao, Chaoxian; Goh, Tian -Wei; Brashler, Kyle; Gustafson, Jeffrey A.; Huang, Wenyu

    2015-09-11

    Metal nanostructures have attracted great attention in various fields due to their tunable properties through precisely tailored sizes, compositions and structures. Using mesoporous silica (mSiO2) as the inorganic capping agent and encapsulated Pt nanoparticles as the seeds, we developed a robust seeded growth method to prepare uniform bimetallic nanoparticles encapsulated in mesoporous silica shells (PtM@mSiO2, M = Pd, Rh, Ni and Cu). Unexpectedly, we found that the inorganic silica shell is able to accommodate an eight-fold volume increase in the metallic core by reducing its thickness. The bimetallic nanoparticles encapsulated in mesoporous silica shells showed enhanced catalytic properties and thermal stabilities compared with those prepared with organic capping agents. As a result, this inorganic capping strategy could find a broad application in the synthesis of versatile bimetallic nanostructures with exceptional structural control and enhanced catalytic properties.

  12. An inorganic capping strategy for the seeded growth of versatile bimetallic nanostructures

    DOE PAGES

    Pei, Yuchen; Maligal-Ganesh, Raghu V.; Xiao, Chaoxian; Goh, Tian -Wei; Brashler, Kyle; Gustafson, Jeffrey A.; Huang, Wenyu

    2015-09-11

    Metal nanostructures have attracted great attention in various fields due to their tunable properties through precisely tailored sizes, compositions and structures. Using mesoporous silica (mSiO2) as the inorganic capping agent and encapsulated Pt nanoparticles as the seeds, we developed a robust seeded growth method to prepare uniform bimetallic nanoparticles encapsulated in mesoporous silica shells (PtM@mSiO2, M = Pd, Rh, Ni and Cu). Unexpectedly, we found that the inorganic silica shell is able to accommodate an eight-fold volume increase in the metallic core by reducing its thickness. The bimetallic nanoparticles encapsulated in mesoporous silica shells showed enhanced catalytic properties and thermalmore » stabilities compared with those prepared with organic capping agents. As a result, this inorganic capping strategy could find a broad application in the synthesis of versatile bimetallic nanostructures with exceptional structural control and enhanced catalytic properties.« less

  13. An inorganic capping strategy for the seeded growth of versatile bimetallic nanostructures

    NASA Astrophysics Data System (ADS)

    Pei, Yuchen; Maligal-Ganesh, Raghu V.; Xiao, Chaoxian; Goh, Tian-Wei; Brashler, Kyle; Gustafson, Jeffrey A.; Huang, Wenyu

    2015-10-01

    Metal nanostructures have attracted great attention in various fields due to their tunable properties through precisely tailored sizes, compositions and structures. Using mesoporous silica (mSiO2) as the inorganic capping agent and encapsulated Pt nanoparticles as the seeds, we developed a robust seeded growth method to prepare uniform bimetallic nanoparticles encapsulated in mesoporous silica shells (PtM@mSiO2, M = Pd, Rh, Ni and Cu). Unexpectedly, we found that the inorganic silica shell is able to accommodate an eight-fold volume increase in the metallic core by reducing its thickness. The bimetallic nanoparticles encapsulated in mesoporous silica shells showed enhanced catalytic properties and thermal stabilities compared with those prepared with organic capping agents. This inorganic capping strategy could find a broad application in the synthesis of versatile bimetallic nanostructures with exceptional structural control and enhanced catalytic properties.Metal nanostructures have attracted great attention in various fields due to their tunable properties through precisely tailored sizes, compositions and structures. Using mesoporous silica (mSiO2) as the inorganic capping agent and encapsulated Pt nanoparticles as the seeds, we developed a robust seeded growth method to prepare uniform bimetallic nanoparticles encapsulated in mesoporous silica shells (PtM@mSiO2, M = Pd, Rh, Ni and Cu). Unexpectedly, we found that the inorganic silica shell is able to accommodate an eight-fold volume increase in the metallic core by reducing its thickness. The bimetallic nanoparticles encapsulated in mesoporous silica shells showed enhanced catalytic properties and thermal stabilities compared with those prepared with organic capping agents. This inorganic capping strategy could find a broad application in the synthesis of versatile bimetallic nanostructures with exceptional structural control and enhanced catalytic properties. Electronic supplementary information (ESI

  14. Synthesis, Study, and Discrete Dipole Approximation Simulation of Ag-Au Bimetallic Nanostructures

    NASA Astrophysics Data System (ADS)

    Hu, Yang; Zhang, An-Qi; Li, Hui-Jun; Qian, Dong-Jin; Chen, Meng

    2016-04-01

    Water-soluble Ag-Au bimetallic nanostructures were prepared via co-reduction and seed-mediated growth routes employing poly-(4-styrenesulfonic acid-co-maleic acid) (PSSMA) as both a reductant and a stabilizer. Ag-Au alloy nanoparticles were obtained by the co-reduction of AgNO3 and HAuCl4, while Ag-Au core-shell nanostructures were prepared through seed-mediated growth using PSSMA-Au nanoparticle seeds in a heated AgNO3 solution. The optical properties of the Ag-Au alloy and core-shell nanostructures were studied, and the growth mechanism of the bimetallic nanoparticles was investigated. Plasmon resonance bands in the range 422 to 517 nm were observed for Ag-Au alloy nanoparticles, while two plasmon resonances were found in the Ag-Au core-shell nanostructures. Furthermore, discrete dipole approximation theoretical simulation was used to assess the optical property differences between the Ag-Au alloy and core-shell nanostructures. Composition and morphology studies confirmed that the synthesized materials were Ag-Au bimetallic nanostructures.

  15. Synthesis, Study, and Discrete Dipole Approximation Simulation of Ag-Au Bimetallic Nanostructures.

    PubMed

    Hu, Yang; Zhang, An-Qi; Li, Hui-Jun; Qian, Dong-Jin; Chen, Meng

    2016-12-01

    Water-soluble Ag-Au bimetallic nanostructures were prepared via co-reduction and seed-mediated growth routes employing poly-(4-styrenesulfonic acid-co-maleic acid) (PSSMA) as both a reductant and a stabilizer. Ag-Au alloy nanoparticles were obtained by the co-reduction of AgNO3 and HAuCl4, while Ag-Au core-shell nanostructures were prepared through seed-mediated growth using PSSMA-Au nanoparticle seeds in a heated AgNO3 solution. The optical properties of the Ag-Au alloy and core-shell nanostructures were studied, and the growth mechanism of the bimetallic nanoparticles was investigated. Plasmon resonance bands in the range 422 to 517 nm were observed for Ag-Au alloy nanoparticles, while two plasmon resonances were found in the Ag-Au core-shell nanostructures. Furthermore, discrete dipole approximation theoretical simulation was used to assess the optical property differences between the Ag-Au alloy and core-shell nanostructures. Composition and morphology studies confirmed that the synthesized materials were Ag-Au bimetallic nanostructures. PMID:27094823

  16. Plasmonic Properties of Bimetallic Nanostructures and Their Applications in Hydrogen Sensing and Chemical Reactions

    NASA Astrophysics Data System (ADS)

    Jiang, Ruibin

    Noble metal nanocrystals have attracted great interest from a wide range of research fields because of their intriguing properties endowed by their localized surface plasmon resonances, which are the collective oscillations of free electrons. Under resonant excitation, metal nanostructures exhibit very large scattering and absorption cross sections and large near-field enhancement. These extraordinary properties can be used in different applications, such as plasmonic sensing and imaging, plasmon-controlled optics, photothermal therapy, photocatalysis, solar cells, and so on. Gold and Silver nanocrystals have plasmon resonances in the visible and near-infrared regions. However, gold and silver are not suitable for some applications. For example, they are generally inactive for catalyzing chemical reactions. The integration of plasmonic metals with other metals can offer superior or new physical/chemical properties. In this thesis, I prepared Au/Ag and Au/Pd bimetallic nanostructures and studied their plasmonic properties and applications in hydrogen sensing and photocatalysis. Seeds have a crucial importance in the synthesis of bimetallic nanostructures. I therefore first studied the roles of the crystalline structure and shape of seeds on the overgrowth of bimetallic nanostructures. The overgrowth of silver and palladium on single crystalline Au nanorods, multicrystalline Au nanorods, and nanobipyramids were studied under the same conditions for each metal. The growths of silver and palladium on single crystalline Au nanorods gave cuboidal nanostructures, while rod-shaped nanostructures were obtained from the growths of silver and palladium on multicrystalline Au nanorods and nanobipyramids. Moreover, the growths of silver and palladium on multicrystalline Au nanobipyramids started at the stepped side facets, while the growths started at the twin boundaries on multicrystalline Au nanorods. These results unambiguously indicate that the crystalline structure of

  17. Controlling Bimetallic Nanostructures by the Microemulsion Method with Subnanometer Resolution Using a Prediction Model.

    PubMed

    Buceta, David; Tojo, Concha; Vukmirovic, Miomir B; Deepak, Francis Leonard; López-Quintela, M Arturo

    2015-07-14

    We present a theoretical model to predict the atomic structure of Au/Pt nanoparticles synthesized in microemulsions. Excellent concordance with the experimental results shows that the structure of the nanoparticles can be controlled at subnanometer resolution simply by changing the reactant concentration. The results of this study not only offer a better understanding of the complex mechanisms governing reactions in microemulsions, but open up a simple new way to synthesize bimetallic nanoparticles with ad hoc controlled nanostructures.

  18. Nanoengineering a library of metallic nanostructures using a single microfluidic reactor.

    PubMed

    Sebastián, Víctor; Jensen, Klavs F

    2016-08-18

    Microfluidic synthesis in a microfabricated reactor enables fast and facile synthesis of a wide library of metallic nanostructures: monometallic, bimetallic, anisotropic growth and heterostructures. Specific nanostructures are realized by selection of flow pattern and synthesis parameters. The technique is shown to have advantages over conventional batch technologies. Not only does it allow faster scalable synthesis, but also realization of nanostructures hitherto not reported such as Pt-Ru, Pt-Ni and Pt-Co nanodendrites, Pt-Pd heterostructures, Ag-Pd core-shell NPs, Au-Pd nanodumbbells and Au-Pd nanosheets. PMID:27500728

  19. Chemisorption effects on the spatial atomic distribution of bimetallic nanostructures

    NASA Astrophysics Data System (ADS)

    Montejano-Carrizales, J. M.; Morán-López, J. L.

    1992-04-01

    The spatial atomic distribution in icosahedral and cubo-octahedral bimetallic clusters with a total number of atoms, N=55 and 147, in the presence of chemisorbed species, is studied. The equilibrium atomic configuration is obtained by calculating the free energy within the regular solution model and by assuming that the surface of the cluster is covered by chemisorbed atoms. Depending on the interaction between chemisorbed species and the cluster components, the atomic distribution in the cluster can be completely modified as compared to the case of clusters with a clean surface. Applications to the chemisorption of H and O on CuNi, CuPd, and NiPt clusters are discussed. We present results for the temperature dependence of the concentration at the different shells around the central atom.

  20. Asymmetric AgPd-AuNR heterostructure with enhanced photothermal performance and SERS activity

    NASA Astrophysics Data System (ADS)

    Zhang, Han; Liu, Zeke; Kang, Xiaolin; Guo, Jun; Ma, Wanli; Cheng, Si

    2016-01-01

    Most as-reported nanostructures through galvanic replacement reactions are still symmetric hollow structures, until now. Asymmetric structures fabricated through a galvanic replacement reaction have been rarely reported. However, asymmetric heterostructures can generally lead to new intriguing properties through asymmetric synergistic coupling. Here, we report a simple synthesis of an asymmetric one-ended AgPd bimetal on Au nanorods (AuNR) by combining a galvanic replacement reaction with an Ostwald ripening process. The morphological evolution from a nanodumbbell to a dandelion structure is thoroughly investigated. The unique asymmetric AgPd-AuNR heterostructures possess the required plasmonic performance and avoid strong damping caused by the poor plasmonic metal Pd, resulting in a superior photothermal heating performance and enhanced SERS sensitivity for in situ monitoring of a catalytic reaction compared with the symmetric counterparts.Most as-reported nanostructures through galvanic replacement reactions are still symmetric hollow structures, until now. Asymmetric structures fabricated through a galvanic replacement reaction have been rarely reported. However, asymmetric heterostructures can generally lead to new intriguing properties through asymmetric synergistic coupling. Here, we report a simple synthesis of an asymmetric one-ended AgPd bimetal on Au nanorods (AuNR) by combining a galvanic replacement reaction with an Ostwald ripening process. The morphological evolution from a nanodumbbell to a dandelion structure is thoroughly investigated. The unique asymmetric AgPd-AuNR heterostructures possess the required plasmonic performance and avoid strong damping caused by the poor plasmonic metal Pd, resulting in a superior photothermal heating performance and enhanced SERS sensitivity for in situ monitoring of a catalytic reaction compared with the symmetric counterparts. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07333b

  1. Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Repo, Eveliina; Heikkilä, Mikko; Leskelä, Markku; Sillanpää, Mika

    2010-10-01

    Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), ξ-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH2OH·HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H2PtCl6 to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

  2. Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template.

    PubMed

    Liu, Wei; Repo, Eveliina; Heikkilä, Mikko; Leskelä, Markku; Sillanpää, Mika

    2010-10-01

    Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), xi-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH(2)OH.HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H(2)PtCl(6) to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

  3. Improving Light Harvesting in Dye-Sensitized Solar Cells Using Hybrid Bimetallic Nanostructures

    DOE PAGES

    Zarick, Holly F.; Erwin, William R.; Boulesbaa, Abdelaziz; Hurd, Olivia K.; Webb, Joseph A.; Puretzky, Alexander A.; Geohegan, David B.; Bardhan, Rizia

    2016-01-25

    In this paper, we demonstrate improved light trapping in dye-sensitized solar cells (DSSCs) with hybrid bimetallic gold core/silver shell nanostructures. Silica-coated bimetallic nanostructures (Au/Ag/SiO2 NSs) integrated in the active layer of DSSCs resulted in 7.51% power conversion efficiency relative to 5.97% for reference DSSCs, giving rise to 26% enhancement in device performance. DSSC efficiencies were governed by the particle density of Au/Ag/SiO2 NSs with best performing devices utilizing only 0.44 wt % of nanostructures. We performed transient absorption spectroscopy of DSSCs with variable concentrations of Au/Ag/SiO2 NSs and observed an increase in amplitude and decrease in lifetime with increasing particlemore » density relative to reference. Finally, we attributed this trend to plasmon resonant energy transfer and population of the singlet excited states of the sensitizer molecules at the optimum concentration of NSs promoting enhanced exciton generation and rapid charge transfer into TiO2.« less

  4. Controlling bimetallic nanostructures by the microemulsion method with subnanometer resolution using a prediction model

    DOE PAGES

    Buceta, David; Tojo, Concha; Vukmirovic, Miomir B.; Deepak, F. Leonard; Lopez-Quintela, M. Arturo

    2015-06-02

    In this study, we present a theoretical model to predict the atomic structure of Au/Pt nanoparticles synthesized in microemulsions. Excellent concordance with the experimental results shows that the structure of the nanoparticles can be controlled at sub-nanometer resolution simply by changing the reactants concentration. The results of this study not only offer a better understanding of the complex mechanisms governing reactions in microemulsions, but open up a simple new way to synthesize bimetallic nanoparticles with ad-hoc controlled nanostructures.

  5. Insight into the Catalytic Mechanism of Bimetallic Platinum–Copper Core–Shell Nanostructures for Nonaqueous Oxygen Evolution Reactions

    SciTech Connect

    Ma, Lu; Luo, Xiangyi; Kropf, A. Jeremy; Wen, Jianguo; Wang, Xiaoping; Lee, Sungsik; Myers, Deborah J.; Miller, Dean; Wu, Tianpin; Lu, Jun; Amine, Khalil

    2016-01-01

    The oxygen evolution reaction (OER) plays a critical role in multiple energy conversion and storage applications. However, its sluggish kinetics usually results in large voltage polarization and unnecessary energy loss. Therefore, designing efficient catalysts that could facilitate this process has become an emerging topic. Here, we present a unique Pt–Cu core–shell nanostructure for catalyzing the nonaqueous OER. The catalysts were systematically investigated with comprehensive spectroscopic techniques, and applied in nonaqueous Li–O2 electrochemical cells, which exhibited dramatically reduced charging overpotential (<0.2 V). The superior performance is explained by the robust Cu(I) surface sites stabilized by the Pt core in the nanostructure. The insights into the catalytic mechanism of the unique Pt–Cu core–shell nanostructure gained in this work are expected to serve as a guide for future design of other nanostructured bimetallic OER catalysts.

  6. A photoactive bimetallic framework for direct aminoformylation of nitroarenes

    EPA Science Inventory

    A bimetallic catalyst, AgPd@g-C3N4, was synthesized by immobilizing silver and palladium nanoparticles over the surface of graphitic carbon nitride (g-C3N4) and its utility was demonstrated for the concerted aminoformylation of aromatic nitro compounds under visible light conditi...

  7. Study of Chemistry and Structure-Property Relationship on Tunable Plasmonic Nanostructures

    NASA Astrophysics Data System (ADS)

    Jing, Hao

    -resolved plasmon-enhanced spectroscopic measurements, such as surface-enhanced Raman scattering (SERS). Last but not least, I have demonstrated that the capability of geometry control over Ag-Pd bimetallic hollow nanostructures through nanoscale galvanic replacement can be greatly enhanced by the use of appropriate mild reducing agents, such as ascorbic acid and formaldehyde. With the aid of mild reducing agents, we have been able to fine-tailor the compositions, interior architectures, and surface morphologies of Ag-Pd bimetallic hollow nanoparticles with increased structural complexity through surface ligand-free galvanic replacement processes at room temperature. This reducing agent-mediated galvanic replacement provides a unique way of achieving both enhanced optical tunability and optimized catalytic activities through deliberate control over the geometries of complex Ag-Pd bimetallic nanoparticles.

  8. Groundstates in AgPd using cluster expansion methods

    NASA Astrophysics Data System (ADS)

    Nelson, Lance; Hart, Gus

    2010-03-01

    Palladium alloys have applications in electronics, catalysis, hydrogen storage, and jewelry. The appearance of ordered phases can improve the materials properties for some applications. We present a study of the Ag-Pd system, which is of current interest in electronics and jewelry. We use a model Hamiltonian to quickly search large sets of derivative superstructures for ground states. The model Hamiltonian allows us to perform Monte Carlo simulations to determine transition temperatures. Previous predictions show two unusual ground states: L11, which has only been observed in Cu-Pt, and a new structure (never observed in any other system) with a 1:3 stoichiometry (dubbed L13). We find that L13 is actually unstable. We also predict the ordering temperature for the L11 phase.

  9. Ion beam mixing in Ag-Pd alloys

    NASA Astrophysics Data System (ADS)

    Klatt, J. L.; Averback, R. S.; Peak, David

    1989-09-01

    Ion beam mixing during 750 keV Kr+ irradiation at 80 K was measured on a series of Ag-Pd alloys using Au marker atoms. The mixing in pure Ag was the greatest and it decreased monotonically with increasing Pd content, being a factor of 10 higher in pure Ag than in pure Pd. This large difference in mixing cannot be explained by the difference in cohesion energy between Ag and Pd in the thermodynamic model of ion beam mixing proposed by Johnson et al. [W. L. Johnson, Y. T. Cheng, M. Van Rossum, and M-A. Nicolet, Nucl. Instrum. Methods B 7/8, 657 (1985)]. An alternative model based on local melting in the cascade is shown to account for the ion beam mixing results in Ag and Pd.

  10. Fabrication of ultra-thin nanostructured bimetallic foils by Accumulative Roll Bonding and Asymmetric Rolling

    PubMed Central

    Yu, Hailiang; Lu, Cheng; Tieu, A. Kiet; Godbole, Ajit; Su, Lihong; Sun, Yong; Liu, Mao; Tang, Delin; Kong, Charlie

    2013-01-01

    This paper reports a new technique that combines the features of Accumulative Roll Bonding (ARB) and Asymmetric Rolling (AR). This technique has been developed to enable production of ultra-thin bimetallic foils. Initially, 1.5 mm thick AA1050 and AA6061 foils were roll-bonded using ARB at 200°C, with 50% reduction. The resulting 1.5 mm bimetallic foil was subsequently thinned to 0.04 mm through four AR passes at room temperature. The speed ratio between the upper and lower AR rolls was 1:1.3. The tensile strength of the bimetallic foil was seen to increase with reduction in thickness. The ductility of the foil was seen to reduce upon decreasing the foil thickness from 1.5 mm to 0.14 mm, but increase upon further reduction in thickness from 0.14 mm to 0.04 mm. The grain size was about 140 nm for the AA6061 layer and 235 nm for the AA1050 layer, after the third AR pass. PMID:23918002

  11. Selective Growth of Ag Nanodewdrop on Au Nanostructure: A New Type of Bimetallic Heterostructure

    PubMed Central

    Gao, Li

    2009-01-01

    A new type of bimetallic Au-Ag heterostructured material was prepared by a selective growing strategy of Ag nanodewdrop on the petal tip of Au flower using electrochemical method. The whole process was strictly controlled by forming the reactive tip of flower petal and passivating the facet along the body of metal petal using poly(vinyl pyrrolidone)(PVP) coating film. The formed Au-Ag HSFs were observed to be about 2 μm in diameter and have the Ag particles of about 50 nm settled on the tips of Au petals. The Au-Ag HSFs were found to display the superior properties on the surface-enhanced Raman scattering (SERS). The presence of Ag nanodewdrops could also facilitate the oxidation of Ru(bpy)32+ complex in electrogenerated chemiluminescence (ECL) measurements and dramatically enhance the emission intensity. The features of Au-Ag HSFs can promise a new type of heterogeneous bimetallic alloy material for the potential applications in chemical and biological sensors. PMID:19788230

  12. Polarization-sensitive photocurrent in the resistive Ag/Pd films

    NASA Astrophysics Data System (ADS)

    Saushin, A. S.; Zonov, R. G.; Mikheev, K. G.; Shamshetdinov, R. R.; Mikheev, G. M.

    2016-08-01

    We report on the observation of helicity dependent photocurrent of the 20 μm thick silver-palladium (Ag/Pd) films manufactured by the thick-film technology. The transverse photocurrent is observed at oblique incidence of laser radiation with different wavelengths in the spectral range of 266 - 2100 nm. At the wavelength range of 532 - 2100 nm the polarity of the transverse photocurrent is positive (negative) for the left- (right-) circular polarized beam. We show that action of high temperature on the films in vacuum results in the decrease of longitudinal photocurrent due to the reduction of PdO content. The photon drag effect is suggested to be the origin of the polarization-sensitive photocurrent in the Ag/Pd films. The obtained results show that the Ag/Pd resistive films may be of interest for polarization- sensitive measurements.

  13. M-Au/TiO2 (M = Ag, Pd, and Pt) nanophotocatalyst for overall solar water splitting: role of interfaces.

    PubMed

    Melvin, Ambrose A; Illath, Kavya; Das, Tanmay; Raja, Thirumalaiswamy; Bhattacharyya, Somnath; Gopinath, Chinnakonda S

    2015-08-28

    M-Au/TiO2 (M = Ag, Pd, Pt) composites were prepared through a facile one-pot photodeposition synthesis and evaluated for solar water splitting (SWS) with and without a sacrificial agent. The M-Au combination exhibits a dominant role in augmenting the H2 generation activity by forming a bi-metallic system. Degussa P25 was used as a TiO2 substrate to photodeposit Au followed by Au + M (M = Ag/Pd/Pt). The SWS activity of the M-Au/TiO2 was determined through photocatalytic H2 production in the presence of methanol as a sacrificial agent under one sun conditions with an AM1.5 filter. The highest H2 yield was observed for Pt0.5-Au1/TiO2 and was around 1.3 ± 0.07 mmol h(-1) g(-1), with an apparent quantum yield (AQY) of 6.4%. Pt0.5-Au1/TiO2 also demonstrated the same activity for 25 cycles of five hours each for 125 h. Critically, the same Pt0.5-Au1/TiO2 catalyst was active in overall SWS (OSWS) without any sacrificial agent, with an AQY = 0.8%. The amount of Au and/or Pt was varied to obtain the optimum composition and it was found that the Pt0.5-Au1/TiO2 composition exhibits the best activity. Detailed characterization by physico-chemical, spectral and microscopy measurements was carried out to obtain an in-depth understanding of the origin of the photocatalytic activity of Pt0.5-Au1/TiO2. These in-depth studies show that gold interacts predominantly with oxygen vacancies present on titania surfaces, and Pt preferentially interacts with gold for an effective electron-hole pair separation at Pt-Au interfaces and electron storage in metal particles. The Pt in Pt0.5-Au1/TiO2 is electronically and catalytically different from the Pt in Pt/TiO2 and it is predicted that the former suppresses the oxygen reduction reaction. PMID:26199221

  14. Deformation-induced nanoscale mixing reactions in Cu/Ni and Ag/Pd multilayers

    SciTech Connect

    Wang, Z.; Perepezko, J. H.

    2013-11-04

    During the repeated cold rolling of Cu/Ni and Ag/Pd multilayers, a solid solution forms at the interfaces as nanoscale layer structure with a composition that replicates the overall multilayer composition. The interfacial mixing behavior was investigated by means of X-ray diffraction and scanning transmission electron microscopy. During deformation induced reaction, the intermixing behavior of the Cu/Ni and Ag/Pd multilayers is in contrast to thermally activated diffusion behavior. This distinct behavior can provide new kinetic pathways and offer opportunities for microstructure control that cannot be achieved by thermal processing.

  15. M-Au/TiO2 (M = Ag, Pd, and Pt) nanophotocatalyst for overall solar water splitting: role of interfaces

    NASA Astrophysics Data System (ADS)

    Melvin, Ambrose A.; Illath, Kavya; Das, Tanmay; Raja, Thirumalaiswamy; Bhattacharyya, Somnath; Gopinath, Chinnakonda S.

    2015-08-01

    M-Au/TiO2 (M = Ag, Pd, Pt) composites were prepared through a facile one-pot photodeposition synthesis and evaluated for solar water splitting (SWS) with and without a sacrificial agent. The M-Au combination exhibits a dominant role in augmenting the H2 generation activity by forming a bi-metallic system. Degussa P25 was used as a TiO2 substrate to photodeposit Au followed by Au + M (M = Ag/Pd/Pt). The SWS activity of the M-Au/TiO2 was determined through photocatalytic H2 production in the presence of methanol as a sacrificial agent under one sun conditions with an AM1.5 filter. The highest H2 yield was observed for Pt0.5-Au1/TiO2 and was around 1.3 +/- 0.07 mmol h-1 g-1, with an apparent quantum yield (AQY) of 6.4%. Pt0.5-Au1/TiO2 also demonstrated the same activity for 25 cycles of five hours each for 125 h. Critically, the same Pt0.5-Au1/TiO2 catalyst was active in overall SWS (OSWS) without any sacrificial agent, with an AQY = 0.8%. The amount of Au and/or Pt was varied to obtain the optimum composition and it was found that the Pt0.5-Au1/TiO2 composition exhibits the best activity. Detailed characterization by physico-chemical, spectral and microscopy measurements was carried out to obtain an in-depth understanding of the origin of the photocatalytic activity of Pt0.5-Au1/TiO2. These in-depth studies show that gold interacts predominantly with oxygen vacancies present on titania surfaces, and Pt preferentially interacts with gold for an effective electron-hole pair separation at Pt-Au interfaces and electron storage in metal particles. The Pt in Pt0.5-Au1/TiO2 is electronically and catalytically different from the Pt in Pt/TiO2 and it is predicted that the former suppresses the oxygen reduction reaction.M-Au/TiO2 (M = Ag, Pd, Pt) composites were prepared through a facile one-pot photodeposition synthesis and evaluated for solar water splitting (SWS) with and without a sacrificial agent. The M-Au combination exhibits a dominant role in augmenting the H2

  16. Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction

    PubMed Central

    Chen, Dong; Ye, Feng; Liu, Hui; Yang, Jun

    2016-01-01

    Precisely tailoring the structure and fully making use of the components of nanoparticles are effective to enhance their catalytic performance for a given reaction. We herein demonstrate the design of cage-bell structured Pt-Pd nanoparticles, where a Pd shell is deliberately selected to enhance the catalytic property and methanol tolerance of Pt for oxygen reduction reaction. This strategy starts with the synthesis of core-shell Pt@Ag nanoparticles, followed by galvanic replacement reaction between the Ag shell and Pd2+ ions to form core-shell-shell Pt@Ag@Ag-Pd nanoparticles with a Pt core and double shells composed of Ag at inner and alloy Ag-Pd at outer, respectively. Then, the core-shell-shell templates are agitated with saturated NaCl solution to eliminate the Ag component from the double shells, leading to the formation of bimetallic Pt-Pd nanoparticles with a cage-bell structure, defined as a movable Pt core enclosed by a porous Pd shell, which show enhanced catalytic activity for oxygen reduction compared with that of the Pt seeds due to the additional catalysis from Pd shell. In addition, owing to the different diffusion behavior of methanol and oxygen molecules in the porous Pd shell, the Pt-Pd cage-bell nanostructures also exhibit superior methanol tolerant property in catalyzing the oxygen reduction. PMID:27079897

  17. Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction.

    PubMed

    Chen, Dong; Ye, Feng; Liu, Hui; Yang, Jun

    2016-01-01

    Precisely tailoring the structure and fully making use of the components of nanoparticles are effective to enhance their catalytic performance for a given reaction. We herein demonstrate the design of cage-bell structured Pt-Pd nanoparticles, where a Pd shell is deliberately selected to enhance the catalytic property and methanol tolerance of Pt for oxygen reduction reaction. This strategy starts with the synthesis of core-shell Pt@Ag nanoparticles, followed by galvanic replacement reaction between the Ag shell and Pd(2+) ions to form core-shell-shell Pt@Ag@Ag-Pd nanoparticles with a Pt core and double shells composed of Ag at inner and alloy Ag-Pd at outer, respectively. Then, the core-shell-shell templates are agitated with saturated NaCl solution to eliminate the Ag component from the double shells, leading to the formation of bimetallic Pt-Pd nanoparticles with a cage-bell structure, defined as a movable Pt core enclosed by a porous Pd shell, which show enhanced catalytic activity for oxygen reduction compared with that of the Pt seeds due to the additional catalysis from Pd shell. In addition, owing to the different diffusion behavior of methanol and oxygen molecules in the porous Pd shell, the Pt-Pd cage-bell nanostructures also exhibit superior methanol tolerant property in catalyzing the oxygen reduction. PMID:27079897

  18. Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Chen, Dong; Ye, Feng; Liu, Hui; Yang, Jun

    2016-04-01

    Precisely tailoring the structure and fully making use of the components of nanoparticles are effective to enhance their catalytic performance for a given reaction. We herein demonstrate the design of cage-bell structured Pt-Pd nanoparticles, where a Pd shell is deliberately selected to enhance the catalytic property and methanol tolerance of Pt for oxygen reduction reaction. This strategy starts with the synthesis of core-shell Pt@Ag nanoparticles, followed by galvanic replacement reaction between the Ag shell and Pd2+ ions to form core-shell-shell Pt@Ag@Ag-Pd nanoparticles with a Pt core and double shells composed of Ag at inner and alloy Ag-Pd at outer, respectively. Then, the core-shell-shell templates are agitated with saturated NaCl solution to eliminate the Ag component from the double shells, leading to the formation of bimetallic Pt-Pd nanoparticles with a cage-bell structure, defined as a movable Pt core enclosed by a porous Pd shell, which show enhanced catalytic activity for oxygen reduction compared with that of the Pt seeds due to the additional catalysis from Pd shell. In addition, owing to the different diffusion behavior of methanol and oxygen molecules in the porous Pd shell, the Pt-Pd cage-bell nanostructures also exhibit superior methanol tolerant property in catalyzing the oxygen reduction.

  19. Strong improvements of localized surface plasmon resonance sensitivity by using Au/Ag bimetallic nanostructures modified with polydopamine films.

    PubMed

    Jia, Kun; Khaywah, Mohammad Y; Li, Yugang; Bijeon, Jean L; Adam, Pierre M; Déturche, Régis; Guelorget, Bruno; François, Manuel; Louarn, Guy; Ionescu, Rodica E

    2014-01-01

    In the present work, the standard monometallic localized surface plasmon resonance (LSPR) biosensing sensitivity is highly improved when using a new system based on glass substrates modified with high-temperature annealed gold/silver bimetallic nanoparticles (Au/Ag bimetallic NPs) coated with polydopamine films before biomolecule specific immobilization. Thus, different zones of bimetallic NPs are spatially created onto a glass support thanks to a commercial transmission electron microscopy (TEM) grid marker in combination with two sequential evaporations of continuous films of gold (4 nm) and silver (2 nm) and followed by annealing at 500 °C for 8 h. By using the scanning electron microscopy (SEM), it is found that annealed Au/Ag bimetallic NPs have uniform size and shape distribution that exhibited a sharper well-defined LSPR resonant peak when compared with that of monometallic Au NPs and thereby contributing to an improved sensitivity in LSPR biosensor application. The controlled micropatterns consisting of bimetallic particles are used in the construction of LSPR biochips for high-throughput detection of different concentrations of a model antigen named bovine serum albumin (BSA) on a single glass sample, with a lower limit of detection of 0.01 ng/mL under the optimized conditions.

  20. Site-specific growth of AgPd nanodendrites on highly purified Au bipyramids with remarkable catalytic performance

    NASA Astrophysics Data System (ADS)

    Zhou, Lin; Liu, Zeke; Zhang, Han; Cheng, Si; Fan, Li-Juan; Ma, Wanli

    2014-10-01

    Au nanorods have been extensively explored in various applications as the template for heterogeneous metallic nanostructures. However, Au bipyramids (AuBPs) have been paid much less attention although they possess an intriguing crystalline structure and extremely superior plasmonic properties which are absent in AuNRs. The state-of-the-art synthesis cannot produce pure AuBPs, which has become a major barrier to their various applications like catalysis since purity is often critical for achieving the desired performance. Herein, we have shown a facile approach to obtain large-scale high-purity AuBPs. The purity of AuBPs can be improved from 30 to 50% for the as-synthesized AuBP solution to over 95% for the purified solution. Site-specific growth of AgPd nanodendrites on multiply twinned AuBPs from core-shell to tipped nanostructures was achieved for the first time by coupling a galvanic replacement with a co-reduction process, which show remarkable catalytic activity in the reduction reaction of 4-nitrophenol (4-NP) by NaBH4. The use of ascorbic acid (AA) as a reductant in the co-reduction process and the intriguing crystalline structure of AuBPs play a critical role in forming these unique structures. We believe that this work would provide a general strategy to prepare high-purity AuBP based trimetallic nanostructures, which offers the opportunity for AuBPs to be widely used in catalysis or other plasmonic-effect related applications in the near future.Au nanorods have been extensively explored in various applications as the template for heterogeneous metallic nanostructures. However, Au bipyramids (AuBPs) have been paid much less attention although they possess an intriguing crystalline structure and extremely superior plasmonic properties which are absent in AuNRs. The state-of-the-art synthesis cannot produce pure AuBPs, which has become a major barrier to their various applications like catalysis since purity is often critical for achieving the desired

  1. Contact Resistance of Ti-Si-C-Ag and Ti-Si-C-Ag-Pd Nanocomposite Coatings

    NASA Astrophysics Data System (ADS)

    Sarius, N. G.; Lauridsen, J.; Lewin, E.; Jansson, U.; Högberg, H.; Öberg, Å.; Sarova, G.; Staperfeld, G.; Leisner, P.; Eklund, P.; Hultman, L.

    2012-03-01

    Ti-Si-C-Ag-Pd and Ti-Si-C-Ag nanocomposite coatings were deposited by direct-current magnetron sputtering on Cu substrates with an electroplated Ni layer. Analytical electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy show that the nanocomposites consist of TiC, Ag:Pd, and amorphous SiC. The contact resistance of these coatings against a spherical Au-Co surface was measured for applied contact forces up to 5 N. Ti-Si-C-Ag-Pd coatings with Ag:Pd top coating had ~10 times lower contact resistance at contact forces below 1 N (~10 mΩ at ~0.1 N), and 2 to 3 times lower for contact forces around 5 N (<1 mΩ at 5 N), compared with the Ti-Si-C-Ag coating.

  2. In vitro cytotoxicity of Ag-Pd-Cu-based casting alloys.

    PubMed

    Niemi, L; Hensten-Pettersen, A

    1985-01-01

    The cytotoxicity and its correlation to alloy composition, structure, corrosion, as well as galvanic coupling was studied with 12 Ag-Pd-Cu-type alloys, one conventional type III gold alloy and pure Ag, Cu, and Pd. The agar overlay cell culture technique was used. Single phase binary CuPd alloys were only slightly cytotoxic below a Cu content of 30 wt%. The tested multiphase alloys were all toxic, but no correlation between toxicity and Cu content could be observed. Solid solution annealing increased the cytotoxicity of a multiphase alloy. Exposure of a single phase alloy to an artificial saliva for 1 week prior to the test decreased its cytotoxicity significantly. Galvanic coupling of the alloys through an outer copper wire decreased their cytotoxicity.

  3. Ti-Ag-Pd alloy with good mechanical properties and high potential for biological applications.

    PubMed

    Zadorozhnyy, V Yu; Shi, X; Gorshenkov, M V; Kozak, D S; Wada, T; Louzguine-Luzgin, D V; Inoue, A; Kato, H

    2016-01-01

    Ti-based alloys containing Ag were produced by tilt-casting method and their properties were studied. Even in its as-cast state, Ti94Ag3Pd3 showed relatively high tensile properties, good electrochemical behavior, and good biocompatibility. The relatively good mechanical properties of the as-cast α-Ti-type Ti94Ag3Pd3 alloy (tensile strength up to 850 MPa and elongation of ~10%) can be explained by its severely deformed, fine crystalline structure. The high biocompatibility of Ti94Ag3Pd3 can be explained by the Ag-Pd interaction, which inhibits the release of Ag ions from the surface. Ag, in combination with Pd has no toxic effects and demonstrates useful antimicrobial properties. The Ti94Ag3Pd3 alloy shows a good potential to be applied as a biomedical implant alloy. PMID:27122177

  4. Ti-Ag-Pd alloy with good mechanical properties and high potential for biological applications

    NASA Astrophysics Data System (ADS)

    Zadorozhnyy, V. Yu.; Shi, X.; Gorshenkov, M. V.; Kozak, D. S.; Wada, T.; Louzguine-Luzgin, D. V.; Inoue, A.; Kato, H.

    2016-04-01

    Ti-based alloys containing Ag were produced by tilt-casting method and their properties were studied. Even in its as-cast state, Ti94Ag3Pd3 showed relatively high tensile properties, good electrochemical behavior, and good biocompatibility. The relatively good mechanical properties of the as-cast α-Ti-type Ti94Ag3Pd3 alloy (tensile strength up to 850 MPa and elongation of ~10%) can be explained by its severely deformed, fine crystalline structure. The high biocompatibility of Ti94Ag3Pd3 can be explained by the Ag-Pd interaction, which inhibits the release of Ag ions from the surface. Ag, in combination with Pd has no toxic effects and demonstrates useful antimicrobial properties. The Ti94Ag3Pd3 alloy shows a good potential to be applied as a biomedical implant alloy.

  5. Structural and magnetic phase transitions in CeCu6 -xTx (T =Ag ,Pd )

    NASA Astrophysics Data System (ADS)

    Poudel, L.; de la Cruz, C.; Payzant, E. A.; May, A. F.; Koehler, M.; Garlea, V. O.; Taylor, A. E.; Parker, D. S.; Cao, H. B.; McGuire, M. A.; Tian, W.; Matsuda, M.; Jeen, H.; Lee, H. N.; Hong, T.; Calder, S.; Zhou, H. D.; Lumsden, M. D.; Keppens, V.; Mandrus, D.; Christianson, A. D.

    2015-12-01

    The structural and the magnetic properties of CeCu6 -xAgx (0 ≤x ≤0.85 ) and CeCu6 -xPdx (0 ≤x ≤0.4 ) have been studied using neutron diffraction, resonant ultrasound spectroscopy (RUS), x-ray diffraction measurements, and first principles calculations. The structural and magnetic phase diagrams of CeCu6 -xAgx and CeCu6 -xPdx as a function of Ag/Pd composition are reported. The end member, CeCu6, undergoes a structural phase transition from an orthorhombic (P n m a ) to a monoclinic (P 21/c ) phase at 240 K. In CeCu6 -xAgx , the structural phase transition temperature (Ts) decreases linearly with Ag concentration and extrapolates to zero at xS ≈0.1 . The structural transition in CeCu6 -xPdx remains unperturbed with Pd substitution within the range of our study. The lattice constant b slightly decreases with Ag/Pd doping, whereas a and c increase with an overall increase in the unit cell volume. Both systems, CeCu6 -xAgx and CeCu6 -xPdx , exhibit a magnetic quantum critical point (QCP), at x ≈0.2 and x ≈0.05 , respectively. Near the QCP, long range antiferromagnetic ordering takes place at an incommensurate wave vector (δ10 δ2), where δ1˜0.62 ,δ2˜0.25 ,x =0.125 for CeCu6 -xPdx and δ1˜0.64 ,δ2˜0.3 ,x =0.3 for CeCu6 -xAgx . The magnetic structure consists of an amplitude modulation of the Ce moments which are aligned along the c axis of the orthorhombic unit cell.

  6. Bimetallic Catalysts.

    ERIC Educational Resources Information Center

    Sinfelt, John H.

    1985-01-01

    Chemical reaction rates can be controlled by varying composition of miniscule clusters of metal atoms. These bimetallic catalysts have had major impact on petroleum refining, where work has involved heterogeneous catalysis (reacting molecules in a phase separate from catalyst.) Experimentation involving hydrocarbon reactions, catalytic…

  7. Photochemical synthesis of noble metal (Ag, Pd, Au, Pt) on graphene/ZnO multihybrid nanoarchitectures as electrocatalysis for H2O2 reduction.

    PubMed

    Gu, Hui; Yang, Yan; Tian, Jixiang; Shi, Guoyue

    2013-07-24

    For the first time, a series of noble metal (Ag, Au, Pd, and Pt) nanoparticles (NPs) based on new functional graphene were successfully achieved via UV-assisted photocatalytic reduction by ZnO nanorods. The whole preparation strategy for constructing noble metal deposited graphene sheets/ZnO (GS/ZnO) was elucidated in detail in this work. First, graphene oxide based two-dimensional carbon nanostructures served as a support to disperse ZnO nanorods through a hydrothermal route. The ZnO nanorods were self-assembled onto the surface of graphene sheets, forming GS/ZnO nanocomposite, and the graphene oxide was reduced, yielding reduced graphene sheets in this synthetic procedure. Second, the GS/ZnO films were further employed as supporting materials for the dispersion of metal nanoparticles. Photogenerated electrons from UV-irradiated ZnO were transported across GS to stepwise and respectively reduce v μL metal ions (Ag(+), Pd(2+), AuCl4(-), PtCl6(2-), 20 mg/mL) into metal (Ag, Pd, Au, Pt) NPs at a location distinct from the ZnO anchored site, forming five graphene-based hybrid nanocomposites designated as GS/ZnO, GS/ZnO@Agv, GS/ZnO@Pdv, GS/ZnO@Auv, GS/ZnO@Ptv, respectively. The obtained mutihybrid nanoarchitectured materials were clearly characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). According to the diameters and distribution, the four metal NPs on GS/ZnO were divided into two categories: Ag&Au and Pd&Pt. Their difference was rooted in the rival abilities of gathering electron between graphene and different metal islands in the photochemical reduction process. The electrochemical behaviors of the five resultant hybrid nanocomposites were investigated in H2O2 as well as in potassium ferricyanide (Fe(CN)6(3-/4-)) and displayed distinct electrocatalytic activity. PMID:23790187

  8. Balance of Nanostructure and Bimetallic Interactions in Pt Model Fuel Cell Catalysts: An in Situ XAS and DFT Study

    SciTech Connect

    Friebel, Daniel; Viswanathan, Venkatasubramanian; Miller, Daniel James; Anniyev, Toyli; Ogasawara, Hirohito; Larsen, Ask Hjorth; O'Grady, Christopher P.; Norskov, Jens K.; Nilsson, Anders

    2012-05-31

    We have studied the effect of nanostructuring in Pt monolayer model electrocatalysts on a Rh(111) single-crystal substrate on the adsorption strength of chemisorbed species. In situ high energy resolution fluorescence detection X-ray absorption spectroscopy at the Pt L(3) edge reveals characteristic changes of the shape and intensity of the 'white-line' due to chemisorption of atomic hydrogen (H(ad)) at low potentials and oxygen-containing species (O/OH(ad)) at high potentials. On a uniform, two-dimensional Pt monolayer grown by Pt evaporation in ultrahigh vacuum, we observe a significant destabilization of both H(ad) and O/OH(ad) due to strain and ligand effects induced by the underlying Rh(111) substrate. When Pt is deposited via a wet-chemical route, by contrast, three-dimensional Pt islands are formed. In this case, strain and Rh ligand effects are balanced with higher local thickness of the Pt islands as well as higher defect density, shifting H and OH adsorption energies back toward pure Pt. Using density functional theory, we calculate O adsorption energies and corresponding local ORR activities for fcc 3-fold hollow sites with various local geometries that are present in the three-dimensional Pt islands.

  9. Investigation of the structure of a Ag/Pd/Ag( 1 1 1 ) trilayer by means of electronic spectroscopies

    NASA Astrophysics Data System (ADS)

    Dumont, J.; Ghijsen, J.; Sporken, R.

    2002-06-01

    The growth of the Ag/Pd/Ag system has been studied by X-ray photoelectron spectroscopy and low energy electron diffraction. No chemical reaction or interdiffusion was observed between the Pd and Ag layers. The growth of the Pd interlayer follows the Frank Van der Merwe mode but is not pseudomorphic on the Ag(1 1 1) substrate. The growth of the top Ag layer on the Pd interlayer is pseudomorphic and layer by layer but contains around 12% of voids.

  10. Transparent ITO/Ag-Pd-Cu/ITO multilayer cathode use in inverted organic solar cells

    SciTech Connect

    Kim, Hyo-Joong; Kim, Han-Ki; Lee, Hyun Hwi; Kal, Jinha; Hahn, Jungseok

    2015-10-15

    The characteristics of transparent ITO/Ag-Pd-Cu (APC)/ITO multilayer cathodes were investigated for use in inverted organic solar cells (IOSCs). The insertion of an APC interlayer into the ITO film effectively led to crystallization of the top ITO layer, unlike that in the Ag interlayer, and resulted in a low sheet resistance of 6.55 Ohm/square and a high optical transmittance of 84.14% without post annealing. In addition, the alloying of the Pd and Cu elements into Ag prevented agglomeration and oxidization of the metal interlayer and led to more stable ITO/APC/ITO films under ambient conditions. The microstructure and interfacial structure of the transparent ITO/APC/ITO cathode in the IOSCs were examined in detail by synchrotron X-ray scattering and high resolution transmission electron microscopy. Furthermore, we suggested a possible mechanism to explain the lower PCE of the IOSCs with an ITO/APC/ITO cathode than that of a reference IOSC with a crystalline ITO cathode using the external quantum efficiency of the IOSCs.

  11. Electrospun polyacrylonitrile nanofibers supported Ag/Pd nanoparticles for hydrogen generation from the hydrolysis of ammonia borane

    NASA Astrophysics Data System (ADS)

    Tong, Yan; Lu, Xiaofeng; Sun, Weining; Nie, Guangdi; Yang, Liu; Wang, Ce

    2014-09-01

    A high-performance hydrogen generation system based on the electrospun polyacrylonitrile (PAN)/Ag/Pd composite nanofibers, which were prepared by microwave reducing the electrospun PAN/AgNO3 nanofibers and followed by a replacement reaction has been demonstrated. The morphology of the as-prepared PAN/Ag/Pd composite nanofibers and the metal nanoparticles on the fibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. It has been demonstrated that the obtained PAN/Ag/Pd composite nanofibers possess fine morphology and high catalytic activities for H2 generation from aqueous solution of ammonia borane (NH3BH3, AB). The H2 generation test exhibited that the catalyst had excellent catalytic activity (with turnover frequency (TOF) of 377.2 mol H2 h-1 (mol Pd)-1), good recycle stability and easy-separation from the reaction system. This new kind of nanofibers possesses great potential application for the new clean energy development.

  12. Effect of thione primers on adhesive bonding between an indirect composite material and Ag-Pd-Cu-Au alloy.

    PubMed

    Imai, Hideyuki; Koizumi, Hiroyasu; Shimoe, Saiji; Hirata, Isao; Matsumura, Hideo; Nikawa, Hiroki

    2014-01-01

    The current study evaluated the effect of primers on the shear bond strength of an indirect composite material joined to a silverpalladium-copper-gold (Ag-Pd-Cu-Au) alloy (Castwell). Disk specimens were cast from the alloy and were air-abraded with alumina. Eight metal primers were applied to the alloy surface. A light-polymerized indirect composite material (Solidex) was bonded to the alloy. Shear bond strength was determined both before and after the application of thermocycling. Two groups primed with Metaltite (thione) and M. L. Primer (sulfide) showed the greatest post-thermocycling bond strength (8.8 and 6.5 MPa). The results of the X-ray photoelectron spectroscopic (XPS) analysis suggested that the thione monomer (MTU-6) in the Metaltite primer was strongly adsorbed onto the Ag-Pd-Cu-Au alloy surface even after repeated cleaning with acetone. The application of either the thione (MTU-6) or sulfide primer is effective for enhancing the bonding between a composite material and Ag-Pd-Cu-Au alloy.

  13. Ag-Pd-Cu alloy inserted transparent indium tin oxide electrodes for organic solar cells

    SciTech Connect

    Kim, Hyo-Joong; Seo, Ki-Won; Kim, Han-Ki; Noh, Yong-Jin; Na, Seok-In

    2014-09-01

    The authors report on the characteristics of Ag-Pd-Cu (APC) alloy-inserted indium tin oxide (ITO) films sputtered on a glass substrate at room temperature for application as transparent anodes in organic solar cells (OSCs). The effect of the APC interlayer thickness on the electrical, optical, structural, and morphological properties of the ITO/APC/ITO multilayer were investigated and compared to those of ITO/Ag/ITO multilayer electrodes. At the optimized APC thickness of 8 nm, the ITO/APC/ITO multilayer exhibited a resistivity of 8.55 × 10{sup −5} Ω cm, an optical transmittance of 82.63%, and a figure-of-merit value of 13.54 × 10{sup −3} Ω{sup −1}, comparable to those of the ITO/Ag/ITO multilayer. Unlike the ITO/Ag/ITO multilayer, agglomeration of the metal interlayer was effectively relieved with APC interlayer due to existence of Pd and Cu elements in the thin region of the APC interlayer. The OSCs fabricated on the ITO/APC/ITO multilayer showed higher power conversion efficiency than that of OSCs prepared on the ITO/Ag/ITO multilayer below 10 nm due to the flatness of the APC layer. The improved performance of the OSCs with ITO/APC/ITO multilayer electrodes indicates that the APC alloy interlayer prevents the agglomeration of the Ag-based metal interlayer and can decrease the thickness of the metal interlayer in the oxide-metal-oxide multilayer of high-performance OSCs.

  14. Highly sensitive electrochemical sensing platform for lead ion based on synergetic catalysis of DNAzyme and Au-Pd porous bimetallic nanostructures.

    PubMed

    Zhou, Qian; Lin, Youxiu; Lin, Yuping; Wei, Qiaohua; Chen, Guonan; Tang, Dianping

    2016-04-15

    In this work, a sensitive and specific electrochemical biosensor for lead ion (Pb(2+)) detection was developed by coupling with synergetic catalysis of porous Au-Pd bimetallic nanoparticles and hemin/G-quadruplex-based DNAzyme. In the presence of target Pb(2+), the substrate strand was cleaved and the enzyme strand was released. Subsequently, G-rich DNA-labeled Au-Pd bimetallic nanoparticle was linked with the released enzyme strand through the helper DNA. Upon addition of hemin, a large number of hemin/G-quadruplex-based DNAzyme molecules were formed on the electrode to serve as nicotinamide adenine dinucleotide hydrogen (NADH) oxidase and peroxidase mimics. DNAzyme could catalyzed the reduction of H2O2, generated from NADH in the presence of O2, to produce an electrochemical signal when using thionine as the electron mediator. Introduction of porors Au-Pd bimetallic nanoparticles could enhance the detectable signal and cause the increase in the sensitivity. Experimental results showed that the variations (∆I) in the cathodic peak currents of the biosensor were linearly dependent on target Pb(2+) concentrations from 1.0 pM to 100 nM with a detection limit (LOD) of 0.34 pM. The excellent performance of the sensing platform indicated its promising prospect as a valuable tool for simple and cost-effective Pb(2+) detection in practical application.

  15. Oxidation of ethyl acetate by a high performance nanostructure (Ni, Mn)-Ag/ZSM-5 bimetallic catalysts and development of an artificial neural networks predictive modeling.

    PubMed

    Jodaei, Azadeh; Salari, Darush; Niaei, Ali; Khatamian, Masumeh; Hosseini, Seyed Ali

    2011-01-01

    The catalytic oxidation of ethyl acetate in low concentration was investigated over mono-metallic Ag/ZSM5 and bimetallic (Ni, Mn)-Ag/ZSM-5 catalysts. Catalytic studies were carried out in a catalytic fixed bed reactor under atmospheric pressure. The sequence of catalytic activity was as follows: Ni-Ag-ZSM-5 > Mn-Ag-ZSM-5 > Ag-ZSM-5 > H-ZSM-5. The catalysts were characterized by ICP-AES, X-ray diffraction (XRD), low temperature nitrogen adsorption, NH(3)-TPD, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and diffuse reflectance UV-vis spectra (UV-vis). An artificial neural networks (ANN) model was developed to predict the performance of catalytic oxidation process over bimetallic Ni-Ag/ZSM-5 catalyst based on experimental data. For this purpose the standard feed forward back propagation algorithm was employed to train the model by using laboratory experimental data. A good agreement was resulted between experimental results and those obtained by ANN. Following order for variables effects on conversion yield of ethyl acetate was predicted by ANN model: reaction temperature (32.99%) > Ag loading (27.38%) > initial ethyl acetate concentration (23.58%) > Ni loading (16.05%). PMID:21104495

  16. Structural and magnetic phase transitions in CeCu6-xTx (T = Ag,Pd)

    DOE PAGES

    Poudel, Lekhanath N.; De la cruz, Clarina; Payzant, E. Andrew; Koehler, Michael R.; May, Andrew F.; Garlea, Vasile O.; Taylor, Alice E.; Parker, David S.; Cao, Huibo B.; McGuire, Michael A.; et al

    2015-12-15

    The structural and the magnetic properties of CeCu6-xAgx (0 ≤ x ≤ 0.85) and CeCu6-xPdx (0 ≤ x ≤ 0.4) have been studied using neutron diffraction, resonant ultrasound spectroscopy (RUS), x-ray diffraction measurements, and first principles calculations. The structural and magnetic phase diagrams of CeCu6-xAgx and CeCu6-xPdx as a function of Ag/Pd composition are reported. The end member, CeCu6, undergoes a structural phase transition from an orthorhombic (Pnma) to a monoclinic (P21/c) phase at 240 K. In CeCu6-xAgx, the structural phase transition temperature (Ts) decreases linearly with Ag concentration and extrapolates to zero at xS ≈ 0.1. The structural transitionmore » in CeCu6-xPdx remains unperturbed with Pd substitution within the range of our study. The lattice constant b slightly decreases with Ag/Pd doping, whereas a and c increase with an overall increase in the unit cell volume. Both systems, CeCu6-xAgx and CeCu6-xPdx, exhibit a magnetic quantum critical point (QCP), at x ≈ 0.2 and x ≈ 0.05, respectively. Near the QCP, long range antiferromagnetic ordering takes place at an incommensurate wave vector (δ1 0 δ2), where δ1 ~ 0.62, δ2 ~ 0.25, x = 0.125 for CeCu6-xPdx and δ1 ~ 0.64, δ2 ~ 0.3, x = 0.3 for CeCu6-xAgx. As a result, the magnetic structure consists of an amplitude modulation of the Ce moments which are aligned along the c axis of the orthorhombic unit cell.« less

  17. The effect of metal cluster deposition route on structure and photocatalytic activity of mono- and bimetallic nanoparticles supported on TiO2 by radiolytic method

    NASA Astrophysics Data System (ADS)

    Klein, Marek; Nadolna, Joanna; Gołąbiewska, Anna; Mazierski, Paweł; Klimczuk, Tomasz; Remita, Hynd; Zaleska-Medynska, Adriana

    2016-08-01

    TiO2 (P25) was modified with small and relatively monodisperse mono- and bimetallic clusters (Ag, Pd, Pt, Ag/Pd, Ag/Pt and Pd/Pt) induced by radiolysis to improve its photocatalytic activity. The as-prepared samples were characterized by X-ray fluorescence spectrometry (XRF), photoluminescence spectrometry (PL), diffuse reflectance spectroscopy (DRS), X-ray powder diffractometry (XRD), scanning transition electron microscopy (STEM) and BET surface area analysis. The effect of metal type (mono- and bimetallic modification) as well as deposition method (simultaneous or subsequent deposition of two metals) on the photocatalytic activity in toluene removal in gas phase under UV-vis irradiation (light-emitting diodes- LEDs) and phenol degradation in liquid phase under visible light irradiation (λ > 420 nm) were investigated. The highest photoactivity under Vis light was observed for TiO2 co-loaded with platinum (0.1%) and palladium (0.1%) clusters. Simultaneous addition of metal precursors results in formation of larger metal nanoparticles (15-30 nm) on TiO2 surface and enhances the Vis-induced activity of Ag/Pd-TiO2 up to four times, while the subsequent metal ions addition results in formation of metal particle size ranging from 4 to 20 nm. Subsequent addition of metal precursors results in formation of BNPs (bimetallic nanoparticle) composites showing higher stability in four cycles of toluene degradation under UV-vis. Obtained results indicated that direct electron transfer from the BNPs to the conduction band of the semiconductor is responsible for visible light photoactivity, whereas superoxide radicals (such as O2rad- and rad OOH) are responsible for pollutants degradation over metal-TiO2 composites.

  18. Tunable Catalysis of Water to Peroxide with Anionic, Cationic, and Neutral Atomic Au, Ag, Pd, Rh, and Os

    NASA Astrophysics Data System (ADS)

    Suggs, K.; Kiros, F.; Tesfamichael, A.; Felfli, Z.; Msezane, A. Z.

    2015-05-01

    Fundamental anionic, cationic, and neutral atomic metal predictions utilizing density functional theory calculations validate the recent discovery identifying the interplay between Regge resonances and Ramsauer-Townsend minima obtained through complex angular momentum analysis as the fundamental atomic mechanism underlying nanoscale catalysis. Here we investigate the optimization of the catalytic behavior of Au, Ag, Pd, Rh, and Os atomic systems via polarization effects and conclude that anionic atomic systems are optimal and therefore ideal for catalyzing the oxidation of water to peroxide, with anionic Os being the best candidate. The discovery that cationic systems increase the transition energy barrier in the synthesis of peroxide could be important as inhibitors in controlling and regulating catalysis. These findings usher in a fundamental and comprehensive atomic theoretical framework for the generation of tunable catalytic systems. The ultimate aim is to design giant atomic catalysts and sensors, in the context of the recently synthesized tri-metal Ag@Au@Pt and bimetal Ag@Au nanoparticles for greatly enhanced plasmonic properties and improved chemical stability for chemical and biological sensing. Research was supported by U.S. DOE Office of Basic Energy Sciences.

  19. Core-shell Au@Pd nanoparticles with enhanced catalytic activity for oxygen reduction reaction via core-shell Au@Ag/Pd constructions

    PubMed Central

    Chen, Dong; Li, Chengyin; Liu, Hui; Ye, Feng; Yang, Jun

    2015-01-01

    Core-shell nanoparticles often exhibit improved catalytic properties due to the lattice strain created in these core-shell particles. Herein, we demonstrate the synthesis of core-shell Au@Pd nanoparticles from their core-shell Au@Ag/Pd parents. This strategy begins with the preparation of core-shell Au@Ag nanoparticles in an organic solvent. Then, the pure Ag shells are converted into the shells made of Ag/Pd alloy by galvanic replacement reaction between the Ag shells and Pd2+ precursors. Subsequently, the Ag component is removed from the alloy shell using saturated NaCl solution to form core-shell Au@Pd nanoparticles with an Au core and a Pd shell. In comparison with the core-shell Au@Pd nanoparticles upon directly depositing Pd shell on the Au seeds and commercial Pd/C catalysts, the core-shell Au@Pd nanoparticles via their core-shell Au@Ag/Pd templates display superior activity and durability in catalyzing oxygen reduction reaction, mainly due to the larger lattice tensile effect in Pd shell induced by the Au core and Ag removal. PMID:26144550

  20. Plasmonic emission enhancement of colloidal quantum dots in the presence of bimetallic nanoparticles

    SciTech Connect

    Sadeghi, S. M.; Hatef, A.; Meunier, M.; Nejat, A.; Campbell, Q.

    2014-04-07

    We studied plasmonic features of bimetallic nanostructures consisting of gold nanoisland cores semi-coated with a chromium layer and explored how they influence emission of CdSe/ZnS quantum dots. We showed that, compared with chromium-covered glass substrates without the gold cores, the bimetallic nanostructures could significantly enhance the emission of the quantum dots. We studied the impact of the excitation intensity and thickness of the chromium layer on this process and utilized numerical means to identify the mechanisms behind it. Our results suggest that when the chromium layer is thin, the enhancement process is the result of the bimetallic plasmonic features of the nanostructures. As the chromium layer becomes thick, the impact of the gold cores is screened and the enhancement mostly happens mostly via the field enhancement of chromium nanoparticles in the absence of significant energy transfer from the quantum dots to these nanoparticles.

  1. Structural and magnetic phase transitions in CeCu6-xTx (T = Ag,Pd)

    SciTech Connect

    Poudel, Lekhanath N.; De la cruz, Clarina; Payzant, E. Andrew; Koehler, Michael R.; May, Andrew F.; Garlea, Vasile O.; Taylor, Alice E.; Parker, David S.; Cao, Huibo B.; McGuire, Michael A.; Tian, Wei; Matsuda, Masaaki; Jeen, Hyoung Jeen; Lee, Ho Nyung; Hong, Tao; Calder, Stuart A.; Lumsden, Mark D.; Zhou, Haidong; Keppens, Veerle; Mandrus, D.; Christianson, Andrew D.

    2015-12-15

    The structural and the magnetic properties of CeCu6-xAgx (0 ≤ x ≤ 0.85) and CeCu6-xPdx (0 ≤ x ≤ 0.4) have been studied using neutron diffraction, resonant ultrasound spectroscopy (RUS), x-ray diffraction measurements, and first principles calculations. The structural and magnetic phase diagrams of CeCu6-xAgx and CeCu6-xPdx as a function of Ag/Pd composition are reported. The end member, CeCu6, undergoes a structural phase transition from an orthorhombic (Pnma) to a monoclinic (P21/c) phase at 240 K. In CeCu6-xAgx, the structural phase transition temperature (Ts) decreases linearly with Ag concentration and extrapolates to zero at xS ≈ 0.1. The structural transition in CeCu6-xPdx remains unperturbed with Pd substitution within the range of our study. The lattice constant b slightly decreases with Ag/Pd doping, whereas a and c increase with an overall increase in the unit cell volume. Both systems, CeCu6-xAgx and CeCu6-xPdx, exhibit a magnetic quantum critical point (QCP), at x ≈ 0.2 and x ≈ 0.05, respectively. Near the QCP, long range antiferromagnetic ordering takes place at an incommensurate wave vector (δ1 0 δ2), where δ1 ~ 0.62, δ2 ~ 0.25, x = 0.125 for CeCu6-xPdx and δ1 ~ 0.64, δ2 ~ 0.3, x = 0.3 for CeCu6-xAgx. As a result, the magnetic structure consists of an amplitude modulation of the Ce moments which are aligned along the c axis of the orthorhombic unit cell.

  2. Determination of the compositions of the DIGM zone in nanocrystalline Ag/Au and Ag/Pd thin films by secondary neutral mass spectrometry

    PubMed Central

    Molnár, Gábor Y; Shenouda, Shenouda S; Katona, Gábor L; Langer, Gábor A

    2016-01-01

    Summary Alloying by grain boundary diffusion-induced grain boundary migration is investigated by secondary neutral mass spectrometry depth profiling in Ag/Au and Ag/Pd nanocrystalline thin film systems. It is shown that the compositions in zones left behind the moving boundaries can be determined by this technique if the process takes place at low temperatures where solely the grain boundary transport is the contributing mechanism and the gain size is less than the half of the grain boundary migration distance. The results in Ag/Au system are in good accordance with the predictions given by the step mechanism of grain boundary migration, i.e., the saturation compositions are higher in the slower component (i.e., in Au or Pd). It is shown that the homogenization process stops after reaching the saturation values and further intermixing can take place only if fresh samples with initial compositions, according to the saturation values, are produced and heat treated at the same temperature. The reversal of the film sequence resulted in the reversal of the inequality of the compositions in the alloyed zones, which is in contrast to the above theoretical model, and explained by possible effects of the stress gradients developed by the diffusion processes itself. PMID:27335738

  3. Determination of the compositions of the DIGM zone in nanocrystalline Ag/Au and Ag/Pd thin films by secondary neutral mass spectrometry.

    PubMed

    Molnár, Gábor Y; Shenouda, Shenouda S; Katona, Gábor L; Langer, Gábor A; Beke, Dezső L

    2016-01-01

    Alloying by grain boundary diffusion-induced grain boundary migration is investigated by secondary neutral mass spectrometry depth profiling in Ag/Au and Ag/Pd nanocrystalline thin film systems. It is shown that the compositions in zones left behind the moving boundaries can be determined by this technique if the process takes place at low temperatures where solely the grain boundary transport is the contributing mechanism and the gain size is less than the half of the grain boundary migration distance. The results in Ag/Au system are in good accordance with the predictions given by the step mechanism of grain boundary migration, i.e., the saturation compositions are higher in the slower component (i.e., in Au or Pd). It is shown that the homogenization process stops after reaching the saturation values and further intermixing can take place only if fresh samples with initial compositions, according to the saturation values, are produced and heat treated at the same temperature. The reversal of the film sequence resulted in the reversal of the inequality of the compositions in the alloyed zones, which is in contrast to the above theoretical model, and explained by possible effects of the stress gradients developed by the diffusion processes itself. PMID:27335738

  4. Enzymatic plasmonic engineering of Ag/Au bimetallic nanoshells and their use for sensitive optical glucose sensing.

    PubMed

    He, Haili; Xu, Xiaolong; Wu, Haoxi; Jin, Yongdong

    2012-04-01

    Enzyme works for plasmonic nanostructure: an interesting enzyme-responsive hybrid Ag/Au-GOx bimetallic nanoshell (NS) system is reported, in which control over the enzyme reaction of glucose oxidase (GOx) can automatically fine-tune the morphology (from complete NS to porous NS) and optical properties of the hybrid nanostructure. The phenomenon is further exploited as a new platform for sensitive optical glucose sensing. PMID:22388952

  5. Plasmon-induced broadband fluorescence enhancement on Al-Ag bimetallic substrates

    PubMed Central

    Hao, Qi; Du, Deyang; Wang, Chenxi; Li, Wan; Huang, Hao; Li, Jiaqi; Qiu, Teng; Chu, Paul K.

    2014-01-01

    Surface enhanced fluorescence (SEF) utilizes the local electromagnetic environment to enhance fluorescence from the analyte on the surface of a solid substrate with nanostructures. While the detection sensitivity of SEF is improved with the development of nano-techniques, detection of multiple analytes by SEF is still a challenge due to the compromise between the high enhancing efficiency and broad response bandwidth. In this article, a high-efficiency SEF substrate with broad response bandwidth is obtained by embedding silver in an aluminum film to produce additional bonding and anti-bonding hybridized states. The bimetallic film is fabricated by ion implantation and the ion energy and fluence are tailored to control subsurface location of the fabricated bimetallic nanostructures. The process circumvents the inherent limit of aluminum materials and extends the plasmon band of aluminum from deep UV to visible range. Fluorescence from different dyes excited by 310 nm to 555 nm is enhanced by up to 11 folds on the single bimetallic film and the result is theoretically confirmed by finite-difference time-domain simulations. This work demonstrates that bimetallic film can be used for optical detection of multiple analytes. PMID:25109261

  6. Electrochemical synthesis of fractal bimetallic Cu/Ag nanodendrites for efficient surface enhanced Raman spectroscopy.

    PubMed

    Li, Da; Liu, Jingquan; Wang, Hongbin; Barrow, Colin J; Yang, Wenrong

    2016-09-21

    Here, we for the first time synthesized bimetallic Cu/Ag dendrites on graphene paper (Cu/Ag@G) using a facile electrodeposition method to achieve efficient SERS enhancement. Cu/Ag@G combined the electromagnetic enhancement of Cu/Ag dendrites and the chemical enhancement of graphene. SERS was ascribed to the rough metal surface, the synergistic effect of copper and silver nanostructures and the charge transfer between graphene and the molecules. PMID:27522964

  7. Facile synthesis of ultrathin bimetallic PtSn wavy nanowires by nanoparticle attachment as enhanced hydrogenation catalysts.

    PubMed

    Ding, Jiabao; Bu, Lingzheng; Zhang, Nan; Yao, Jianlin; Huang, Yu; Huang, Xiaoqing

    2015-03-01

    Ultrathin wavy nanowires represent an emerging class of nanostructures that exhibit unique catalytic, magnetic, and electronic properties, but the controlled production of bimetallic wavy nanowires remains a significant challenge. Ultrathin bimetallic PtSn nanowires have been prepared with high yield and featuring a highly wavy structure. Owing to the ultrathin nature and unique electronic properties of these PtSn wavy nanowires, they exhibit improved catalytic performance for the hydrogenation of nitrobenzene, as well as for the hydrogenation of styrene. These results suggest a new strategy to prepare highly active catalysts through defect engineering and can significantly impact broad practical applications. PMID:25603959

  8. Exceptional methanol electro-oxidation activity by bimetallic concave and dendritic Pt-Cu nanocrystals catalysts

    NASA Astrophysics Data System (ADS)

    Wang, Ying-Xia; Zhou, Hui-Jing; Sun, Ping-Chuan; Chen, Tie-Hong

    2014-01-01

    PtCux (x = 1, 2 and 3) bimetallic nanocrystals with concave surface and dendritic morphology were prepared and used as electrocatalysts in methanol oxidation reaction (MOR) for polymer electrolyte membrane fuel cells. The bimetallic nanocrystals were synthesized via one-pot co-reduction of H2PtCl6 and Cu(acac)2 by oleylamine and polyvinyl pyrrolidone (PVP) in an autoclave at 180 °C. The concave dendritic bimetallic nanostructure consisted of a core rich in Cu and nanodendrites rich in Pt, which was formed via galvanic replacement of Cu by Pt. It was found that PVP played an important role in initiating, facilitating, and directing the replacement reaction. The electrochemical properties of the PtCux were characterized by cyclic voltammetry (CV) and chronoamperometry (CA). The concave dendritic PtCu2/C nanocrystals exhibited exceptionally high activity and strong poisoning resistance in MOR. At 0.75 V (vs. reversible hydrogen electrode, RHE) the mass activity and specific activity of PtCu2/C were 3.3 and 4.1 times higher than those of the commercial Pt/C catalysts, respectively. The enhanced catalytic activity could be attributed to the unique concave dendritic morphology of the bimetallic nanocrystals.

  9. Bimetallic nanoparticles for arsenic detection.

    PubMed

    Moghimi, Nafiseh; Mohapatra, Mamata; Leung, Kam Tong

    2015-06-01

    Effective and sensitive monitoring of heavy metal ions, particularly arsenic, in drinking water is very important to risk management of public health. Arsenic is one of the most serious natural pollutants in soil and water in more than 70 countries in the world. The need for very sensitive sensors to detect ultralow amounts of arsenic has attracted great research interest. Here, bimetallic FePt, FeAu, FePd, and AuPt nanoparticles (NPs) are electrochemically deposited on the Si(100) substrate, and their electrochemical properties are studied for As(III) detection. We show that trace amounts of As(III) in neutral pH could be determined by using anodic stripping voltammetry. The synergistic effect of alloying with Fe leads to better performance for Fe-noble metal NPs (Au, Pt, and Pd) than pristine noble metal NPs (without Fe alloying). Limit of detection and linear range are obtained for FePt, FeAu, and FePd NPs. The best performance is found for FePt NPs with a limit of detection of 0.8 ppb and a sensitivity of 0.42 μA ppb(-1). The selectivity of the sensor has also been tested in the presence of a large amount of Cu(II), as the most detrimental interferer ion for As detection. The bimetallic NPs therefore promise to be an effective, high-performance electrochemical sensor for the detection of ultratrace quantities of arsenic.

  10. Bimetallic nanoparticles for arsenic detection.

    PubMed

    Moghimi, Nafiseh; Mohapatra, Mamata; Leung, Kam Tong

    2015-06-01

    Effective and sensitive monitoring of heavy metal ions, particularly arsenic, in drinking water is very important to risk management of public health. Arsenic is one of the most serious natural pollutants in soil and water in more than 70 countries in the world. The need for very sensitive sensors to detect ultralow amounts of arsenic has attracted great research interest. Here, bimetallic FePt, FeAu, FePd, and AuPt nanoparticles (NPs) are electrochemically deposited on the Si(100) substrate, and their electrochemical properties are studied for As(III) detection. We show that trace amounts of As(III) in neutral pH could be determined by using anodic stripping voltammetry. The synergistic effect of alloying with Fe leads to better performance for Fe-noble metal NPs (Au, Pt, and Pd) than pristine noble metal NPs (without Fe alloying). Limit of detection and linear range are obtained for FePt, FeAu, and FePd NPs. The best performance is found for FePt NPs with a limit of detection of 0.8 ppb and a sensitivity of 0.42 μA ppb(-1). The selectivity of the sensor has also been tested in the presence of a large amount of Cu(II), as the most detrimental interferer ion for As detection. The bimetallic NPs therefore promise to be an effective, high-performance electrochemical sensor for the detection of ultratrace quantities of arsenic. PMID:25938763

  11. Fabrication of bimetallic Cu/Au nanotubes and their sensitive, selective, reproducible and reusable electrochemical sensing of glucose

    NASA Astrophysics Data System (ADS)

    Tee, Si Yin; Ye, Enyi; Pan, Pei Hua; Lee, Coryl Jing Jun; Hui, Hui Kim; Zhang, Shuang-Yuan; Koh, Leng Duei; Dong, Zhili; Han, Ming-Yong

    2015-06-01

    Herein, we report a facile two-step approach to produce gold-incorporated copper (Cu/Au) nanostructures through controlled disproportionation of the Cu+-oleylamine complex at 220 °C to form copper nanowires and the subsequent reaction with Au3+ at different temperatures of 140, 220 and 300 °C. In comparison with copper nanowires, these bimetallic Cu/Au nanostructures exhibit their synergistic effect to greatly enhance glucose oxidation. Among them, the shape-controlled Cu/Au nanotubes prepared at 140 °C show the highest electrocatalytic activity for non-enzymatic glucose sensing in alkaline solution. In addition to high sensitivity and fast response, the Cu/Au nanotubes possess high selectivity against interferences from other potential interfering species and excellent reproducibility with long-term stability. By introducing gold into copper nanostructures at a low level of 3, 1 and 0.1 mol% relative to the initial copper precursor, a significant electrocatalytic enhancement of the resulting bimetallic Cu/Au nanostructures starts to occur at 1 mol%. Overall, the present fabrication of stable Cu/Au nanostructures offers a promising low-cost platform for sensitive, selective, reproducible and reusable electrochemical sensing of glucose.Herein, we report a facile two-step approach to produce gold-incorporated copper (Cu/Au) nanostructures through controlled disproportionation of the Cu+-oleylamine complex at 220 °C to form copper nanowires and the subsequent reaction with Au3+ at different temperatures of 140, 220 and 300 °C. In comparison with copper nanowires, these bimetallic Cu/Au nanostructures exhibit their synergistic effect to greatly enhance glucose oxidation. Among them, the shape-controlled Cu/Au nanotubes prepared at 140 °C show the highest electrocatalytic activity for non-enzymatic glucose sensing in alkaline solution. In addition to high sensitivity and fast response, the Cu/Au nanotubes possess high selectivity against interferences from other

  12. Magnetic Compensation in the Bimetallic Oxalates

    SciTech Connect

    Reis, Peter L; Fishman, Randy Scott; Reboredo, Fernando A; Moreno, Juana

    2008-01-01

    Bimetallic oxalates are layered molecule-based magnets with either ferromagnetic or antiferromagnetic interactions between transition metals M(II) and M'(III) on an open honeycomb lattice. Some Fe(II)Fe(III) bimetallic oxalates exhibit magnetic compensation (MC) at a compensation temperature Tcomp ≈ 30 K below the ferrimagnetic transition temperature Tc ≈ 45 K. To see if MC is possible in other bimetallic oxalates, we construct a theoretical model for bimetallic oxalates that exhibit antiferromagnetic interactions. By varying the M(II) and M'(III) average orbital angular momentum, which can be controlled by the choice of interlayer cations, we have found regions of MC in the families M(II)Mn(III) with M = Fe, Co, or Ni and V(II)M'(III) with M' = Cr or V but not in the family M(II)Ru(III) with M = Fe or Cu.

  13. Homogeneous Pt-bimetallic Electrocatalysts

    SciTech Connect

    Wang, Chao; Chi, Miaofang; More, Karren Leslie; Markovic, Nenad; Stamenkovic, Vojislav

    2011-01-01

    Alloying has shown enormous potential for tailoring the atomic and electronic structures, and improving the performance of catalytic materials. Systematic studies of alloy catalysts are, however, often compromised by inhomogeneous distribution of alloying components. Here we introduce a general approach for the synthesis of monodispersed and highly homogeneous Pt-bimetallic alloy nanocatalysts. Pt{sub 3}M (where M = Fe, Ni, or Co) nanoparticles were prepared by an organic solvothermal method and then supported on high surface area carbon. These catalysts attained a homogeneous distribution of elements, as demonstrated by atomic-scale elemental analysis using scanning transmission electron microscopy. They also exhibited high catalytic activities for the oxygen reduction reaction (ORR), with improvement factors of 2-3 versus conventional Pt/carbon catalysts. The measured ORR catalytic activities for Pt{sub 3}M nanocatalysts validated the volcano curve established on extended surfaces, with Pt{sub 3}Co being the most active alloy.

  14. Facile One-Step Synthesis of Three-Dimensional Pd-Ag Bimetallic Alloy Networks and Their Electrocatalytic Activity toward Ethanol Oxidation.

    PubMed

    Fu, Shaofang; Zhu, Chengzhou; Du, Dan; Lin, Yuehe

    2015-07-01

    The three-dimensional palladium networks and palladium-silver bimetallic alloy networks were synthesized at room temperature on a large scale using a rapid and simple strategy. The results revealed that the morphology of the networks is not affected by the composition. We demonstrated that the as-prepared unsupported networks exhibited excellent electrochemical activity and stability toward ethanol oxidation reaction in alkaline media due to the formation of palladium-silver alloys as well as the porous nanostructures. The results indicate that the well-defined three-dimensional palladium-silver bimetallic alloy networks are promising catalysts for fuel cells.

  15. Synthesis and reactivity of new bimetallic oxynitrides

    SciTech Connect

    Oyama, S.T.; Ramanathan, S.; Yu, C.C.

    1995-12-31

    A new series of bimetallic oxynitride catalysts, M{sub 1}M{sub 2}O{sub x}N{sub y} (M{sub 1} = V{sub 1}, Nb, Cr, Mn and Co, M{sub 2} = Mo or W), was prepared by nitriding the bimetallic oxide precursors in an ammonia gas stream at 1000 cm{sup 3}/min (6.8x10{sup 2} {mu}mol s{sup -1}) while the temperature was raised at 5 K/min (8.3x10{sup -2} K s{sup -1}). The catalysts were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, CO chemisorption and surface area measurements. The catalytic activity of these catalysts for mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt% aromatics (15 wt% tetralin and 5 wt% amylbenzene) and balance aliphatics (tetradecane). The activities of the bimetallic oxynitrides were compared to a commercial sulfided Ni-Mo/Al{sub 2}O{sub 3} catalyst tested at the same conditions. The bimetallic oxynitrides were active for quinoline HDN and V-Mo-O-N exhibiting higher HDN activity than the commercial Ni-Mo/Al{sub 2}O{sub 3} catalyst. The HDS activity of the bimetallic oxynitrides ranged from 9-37% with Co-Mo-O-N showing the highest HDS activity among the oxynitrides tested.

  16. Core-size-dependent catalytic properties of bimetallic Au/Ag core-shell nanoparticles.

    PubMed

    Haldar, Krishna Kanta; Kundu, Simanta; Patra, Amitava

    2014-12-24

    Bimetallic core-shell nanoparticles have recently emerged as a new class of functional materials because of their potential applications in catalysis, surface enhanced Raman scattering (SERS) substrate and photonics etc. Here, we have synthesized Au/Ag bimetallic core-shell nanoparticles with varying the core diameter. The red-shifting of the both plasmonic peaks of Ag and Au confirms the core-shell structure of the nanoparticles. Transmission electron microscopy (TEM) analysis, line scan EDS measurement and UV-vis study confirm the formation of core-shell nanoparticles. We have examined the catalytic activity of these core-shell nanostructures in the reaction between 4-nitrophenol (4-NP) and NaBH4 to form 4-aminophenol (4-AP) and the efficiency of the catalytic reaction is found to be increased with increasing the core size of Au/Ag core-shell nanocrystals. The catalytic efficiency varies from 41.8 to 96.5% with varying core size from 10 to 100 nm of Au/Ag core-shell nanoparticles, and the Au100/Ag bimetallic core-shell nanoparticle is found to be 12-fold more active than that of the pure Au nanoparticles with 100 nm diameter. Thus, the catalytic properties of the metal nanoparticles are significantly enhanced because of the Au/Ag core-shell structure, and the rate is dependent on the size of the core of the nanoparticles.

  17. General synthesis of noble metal (Au, Ag, Pd, Pt) nanocrystal modified MoS2 nanosheets and the enhanced catalytic activity of Pd-MoS2 for methanol oxidation.

    PubMed

    Yuwen, Lihui; Xu, Fei; Xue, Bing; Luo, Zhimin; Zhang, Qi; Bao, Biqing; Su, Shao; Weng, Lixing; Huang, Wei; Wang, Lianhui

    2014-06-01

    A general and facile method for water-dispersed noble metal (Au, Ag, Pd, Pt) nanocrystal modified MoS2 nanosheets (NM-MoS2 NSs) has been developed. By using sodium carboxymethyl cellulose as a stabilizer, well-dispersed NM-MoS2 NSs with homogeneously deposited noble metal nanocrystals (NM NCs) can be synthesized in aqueous solutions. Due to the transition from the semiconducting 2H phase to the metallic 1T phase, the chemically exfoliated MoS2 (ce-MoS2) NSs have improved electrochemical activity. The partially metallic nature of the ce-MoS2 NSs and the catalytic activity of the NM NCs synergistically make NM-MoS2 NSs a potential electrochemical catalyst. For the first time, Pd-MoS2 NSs were used as an electrocatalyst for methanol oxidation in alkaline media. The results showed that Pd-MoS2 NSs have enhanced catalytic activity with 2.8-fold anodic peak current mass density compared to a commercial Pd/C catalyst, suggesting potential for application in direct methanol fuel cells (DMFCs).

  18. Doping effect on the Janus-like structure of a copper-iron bimetallic nanocluster and its solid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Taherkhani, Farid; Seresht, Pegah Freshteh

    2015-04-01

    A molecular dynamics simulation with a new-application potential model has been explored for melting temperature, radial distribution of iron-copper bimetallic nanoclusters, and their bulk for the first time. At low copper weight percentages, the melting temperature changes a little for the bulk structures; however, for nanostructures, the variation of melting temperature is significant. At medium copper-doping values, there is a melting-temperature plateau in bimetallic nanoclusters. For many catalysis applications, Janus-like structures are considered, which occur at around 53% iron weight in copper at room temperature, when copper-iron bimetallic nanoclusters clearly consist of two distinct faces. Our result for the melting temperature of the bulk alloy confirms the experimental result.

  19. Reductive dechlorination of trichloroethylene by iron bimetallics

    SciTech Connect

    Orth, R.G.; Dauda, T.; McKenzie, D.E.

    1998-07-01

    Reductive dechlorination using a zero valence metal such as iron has seen an increase in interest with the extension of iron dechlorination to in-situ treatment of ground water. Studies to increase the rate of dechlorination and the long term stability have lead many to examine the use of bimetallic iron systems. Results are shown for bimetallic iron systems of Cu, Sn, Ni, Ag, Au, and Pd. All of these bimetallic couples form a galvanic couple which increase corrosion rates and the production of hydrogen. Increased rates of reaction normalized to surface area were observed for all the couples. The reaction rates were found to depended on surface area and surface coverage of the iron. The results of studies in deuterium oxide indicate that the pathways changed as the bimetallic is changed and that the pathway in all cases could be a combination of dehydrohalgenation and sequential dechlorination. Degradation of DNAPL TCE by iron was found to be zero order and the type of product observed was different from that observed for TCE dissolved in water.

  20. Green synthesis and applications of Au-Ag bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Meena Kumari, M.; Jacob, John; Philip, Daizy

    2015-02-01

    This paper reports for the first time the synthesis of bimetallic nanoparticles at room temperature using the fruit juice of pomegranate. Simultaneous reduction of gold and silver ions in different molar ratios leads to the formation of alloy as well as core-shell nanostructures. The nanoparticles have been characterized using UV-vis spectroscopy, transmission electron microscopy, Fourier Transform Infrared Spectroscopy and X-ray diffraction. The synthesized alloy particles are used as catalysts in the reduction of 2-, 3-, 4-nitrophenols to the corresponding amines and in the degradation of methyl orange. The reduction kinetics for all the reactions follows pseudo-first order. The rate constants follow the order k4-nitrophenol < k2-nitrophenol < k3-nitrophenol. Thermal conductivity is measured as a function of volume fraction and it is observed that the incorporation of the alloy nanoparticles enhances the thermal conductivity of the base fluid (water) showing nanofluid application. The nitric oxide and hydroxyl radical scavenging activity shown by the nanoparticles promise the potential application in biomedical field.

  1. Green synthesis and applications of Au-Ag bimetallic nanoparticles.

    PubMed

    Meena Kumari, M; Jacob, John; Philip, Daizy

    2015-02-25

    This paper reports for the first time the synthesis of bimetallic nanoparticles at room temperature using the fruit juice of pomegranate. Simultaneous reduction of gold and silver ions in different molar ratios leads to the formation of alloy as well as core-shell nanostructures. The nanoparticles have been characterized using UV-vis spectroscopy, transmission electron microscopy, Fourier Transform Infrared Spectroscopy and X-ray diffraction. The synthesized alloy particles are used as catalysts in the reduction of 2-, 3-, 4-nitrophenols to the corresponding amines and in the degradation of methyl orange. The reduction kinetics for all the reactions follows pseudo-first order. The rate constants follow the order k4-nitrophenol

  2. Stainless steel to titanium bimetallic transitions

    NASA Astrophysics Data System (ADS)

    Kaluzny, J. A.; Grimm, C.; Passarelli, D.

    2015-12-01

    In order to use stainless steel piping in an LCLS-II (Linac Coherent Light Source Upgrade) cryomodule, stainless steel to titanium bimetallic transitions are needed to connect the stainless steel piping to the titanium cavity helium vessel. Explosion bonded stainless steel to titanium transition pieces and bimetallic transition material samples have been tested. A sample transition tube was subjected to tests and x-ray examinations between tests. Samples of the bonded joint material were impact and tensile tested at room temperature as well as liquid helium temperature. The joint has been used successfully in horizontal tests of LCLS-II cavity helium vessels and is planned to be used in LCLS-II cryomodules. Results of material sample and transition tube tests will be presented. Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.

  3. Stainless Steel to Titanium Bimetallic Transitions

    SciTech Connect

    Kaluzny, J. A.; Grimm, C.; Passarelli, D.

    2015-01-01

    In order to use stainless steel piping in an LCLS-II (Linac Coherent Light Source Upgrade) cryomodule, stainless steel to titanium bimetallic transitions are needed to connect the stainless steel piping to the titanium cavity helium vessel. Explosion bonded stainless steel to titanium transition pieces and bimetallic transition material samples have been tested. A sample transition tube was subjected to tests and x-ray examinations between tests. Samples of the bonded joint material were impact and tensile tested at room temperature as well as liquid helium temperature. The joint has been used successfully in horizontal tests of LCLS-II cavity helium vessels and is planned to be used in LCLS-II cryomodules. Results of material sample and transition tube tests will be presented.

  4. Bimetallic redox synergy in oxidative palladium catalysis.

    PubMed

    Powers, David C; Ritter, Tobias

    2012-06-19

    Polynuclear transition metal complexes, which are embedded in the active sites of many metalloenzymes, are responsible for effecting a diverse array of oxidation reactions in nature. The range of chemical transformations remains unparalleled in the laboratory. With few noteworthy exceptions, chemists have primarily focused on mononuclear transition metal complexes in developing homogeneous catalysis. Our group is interested in the development of carbon-heteroatom bond-forming reactions, with a particular focus on identifying reactions that can be applied to the synthesis of complex molecules. In this context, we have hypothesized that bimetallic redox chemistry, in which two metals participate synergistically, may lower the activation barriers to redox transformations relevant to catalysis. In this Account, we discuss redox chemistry of binuclear Pd complexes and examine the role of binuclear intermediates in Pd-catalyzed oxidation reactions. Stoichiometric organometallic studies of the oxidation of binuclear Pd(II) complexes to binuclear Pd(III) complexes and subsequent C-X reductive elimination from the resulting binuclear Pd(III) complexes have confirmed the viability of C-X bond-forming reactions mediated by binuclear Pd(III) complexes. Metal-metal bond formation, which proceeds concurrently with oxidation of binuclear Pd(II) complexes, can lower the activation barrier for oxidation. We also discuss experimental and theoretical work that suggests that C-X reductive elimination is also facilitated by redox cooperation of both metals during reductive elimination. The effect of ligand modification on the structure and reactivity of binuclear Pd(III) complexes will be presented in light of the impact that ligand structure can exert on the structure and reactivity of binuclear Pd(III) complexes. Historically, oxidation reactions similar to those discussed here have been proposed to proceed via mononuclear Pd(IV) intermediates, and the hypothesis of mononuclear Pd

  5. Tube-to-header joint for bimetallic construction

    NASA Technical Reports Server (NTRS)

    Lessmann, G. G.; Stoner, D. R.

    1967-01-01

    Design advantages of bimetallic construction enables an all-welded bimetallic joint to be made from the accessible header side of the tube-to-header joint. In the two-piece header design the weld joints completely seal the tube-header plate crevice and prevent crevice and stringer corrosion.

  6. PD/MG BIMETALLIC CORROSION CELLS FOR DECHLORINATING PCBS

    EPA Science Inventory

    Two dissimilar metals immersed in a conducting solution develop different corrosion potentials forming a bimetallic corrosion cell. Enhanced corrosion of an active metal like Mg combined with catalytic hydrogenation properties of a noble metal like Pd in such bimetallic cells can...

  7. The synthesis of Pt/Ag bimetallic nanoparticles using a successive solution plasma process.

    PubMed

    Kim, Sung Min; Lee, Sang Yul; Lee, Min Hyung; Kim, Jung Wan

    2014-12-01

    A successive solution plasma process was developed for the synthesis of Pt/Ag bimetallic nanoparticles. Ag nanoparticles were made first by applying a high voltage of bipolar pulsed DC to anode and cathode electrodes composed of Ag rods. The solution containing Ag nanoparticles was discharged successively using Pt electrodes. The joule heating and electrolysis between electrodes generated vapors, and solution plasma was sustained due to progressive ionization and excitation in the vapor phase. The maximum current and voltage breakdown was observed at approximately 8.9 A and 900 V with an interval of 25 μs, which indicated that an intense solution plasma was sustained continuously. The Pt-on-Ag heterogeneous nanostructures formed, and finally, the Ag nanoparticles were completely covered by Pt nanoparticles after a discharge duration of 1,200 s. PMID:25970983

  8. Pd-Pt Bimetallic Nanodendrites with High Activity for Oxygen Reduction

    SciTech Connect

    Lim, B.; Tao, J.; Jiang, M.; Camargo, P.H.C.; Cho, E.C.; Lu, X.; Zhu, Y.; Xia, Y.

    2009-06-05

    Controlling the morphology of Pt nanostructures can provide a great opportunity to improve their catalytic properties and increase their activity on a mass basis. We synthesized Pd-Pt bimetallic nanodendrites consisting of a dense array of Pt branches on a Pd core by reducing K{sub 2}PtCl{sub 4} with L-ascorbic acid in the presence of uniform Pd nanocrystal seeds in an aqueous solution. The Pt branches supported on faceted Pd nanocrystals exhibited relatively large surface areas and particularly active facets toward the oxygen reduction reaction (ORR), the rate-determining step in a proton-exchange membrane fuel cell. The Pd-Pt nanodendrites were two and a half times more active on the basis of equivalent Pt mass for the ORR than the state-of-the-art Pt/C catalyst and five times more active than the first-generation supportless Pt-black catalyst.

  9. BIMETALLIC LITHIUM BOROHYDRIDES TOWARD REVERSIBLE HYDROGEN STORAGE

    SciTech Connect

    Au, M.

    2010-10-21

    Borohydrides such as LiBH{sub 4} have been studied as candidates for hydrogen storage because of their high hydrogen contents (18.4 wt% for LiBH{sub 4}). Limited success has been made in reducing the dehydrogenation temperature by adding reactants such as metals, metal oxides and metal halides. However, full rehydrogenation has not been realized because of multi-step decomposition processes and the stable intermediate species produced. It is suggested that adding second cation in LiBH{sub 4} may reduce the binding energy of B-H. The second cation may also provide the pathway for full rehydrogenation. In this work, several bimetallic borohydrides were synthesized using wet chemistry, high pressure reactive ball milling and sintering processes. The investigation found that the thermodynamic stability was reduced, but the full rehydrogenation is still a challenge. Although our experiments show the partial reversibility of the bimetallic borohydrides, it was not sustainable during dehydriding-rehydriding cycles because of the accumulation of hydrogen inert species.

  10. Superhydrophilic nanostructure

    DOEpatents

    Mao, Samuel S; Zormpa, Vasileia; Chen, Xiaobo

    2015-05-12

    An embodiment of a superhydrophilic nanostructure includes nanoparticles. The nanoparticles are formed into porous clusters. The porous clusters are formed into aggregate clusters. An embodiment of an article of manufacture includes the superhydrophilic nanostructure on a substrate. An embodiment of a method of fabricating a superhydrophilic nanostructure includes applying a solution that includes nanoparticles to a substrate. The substrate is heated to form aggregate clusters of porous clusters of the nanoparticles.

  11. Modeling the melting temperature of nanoscaled bimetallic alloys.

    PubMed

    Li, Ming; Zhu, Tian-Shu

    2016-06-22

    The effect of size, composition and dimension on the melting temperature of nanoscaled bimetallic alloys was investigated by considering the interatomic interaction. The established thermodynamics model without any arbitrarily adjustable parameters can be used to predict the melting temperature of nanoscaled bimetallic alloys. It is found that, the melting temperature and interatomic interaction of nanoscaled bimetallic alloys decrease with the decrease in size and the increasing composition of the lower surface energy metal. Moreover, for the nanoscaled bimetallic alloys with the same size and composition, the dependence of the melting temperature on the dimension can be sequenced as follows: nanoparticles > nanowires > thin films. The accuracy of the developed model is verified by the recent experimental and computer simulation results.

  12. Neutral bimetallic transition metal phenoxyiminato catalysts and related polymerization methods

    DOEpatents

    Marks, Tobin J.; Rodriguez, Brandon A.; Delferro, Massimiliano

    2012-08-07

    A catalyst composition comprising a neutral bimetallic diphenoxydiiminate complex of group 10 metals or Ni, Pd or Pt is disclosed. The compositions can be used for the preparation of homo- and co-polymers of olefinic monomer compounds.

  13. Bimetallic Nanoshells for Metal - Enhanced Fluorescence with Broad Band Fluorophores.

    PubMed

    Zhang, Jian; Fu, Yi; Mahdavi, Farhad

    2012-11-15

    In this article, we reported the near-field interactions between the Ru(bpy)(3) (2+) complexes and plasmon resonances from the bimetallic nanoshells. The metallic nanoshells were fabricated on 20 nm silica spheres as cores by depositing 10 nm monometallic or bimetallic shells. There were approx. 15 Ru(bpy)(3) (2+) complexes in the silica core. The metal shells were constituted of silver or/and gold. The bimetallic shells could be generated in homogeneous or heterogeneous geometries. The homogeneous bimetallic shells contained 10 nm silver-gold alloys. The heterogeneous bimetallic shells contained successive 5 nm gold and 5 nm silver shells, or alternatively, 5 nm silver and 5 nm gold shells. Optical properties of metal nanoshells were studied on both the ensemble spectra and single nanoparticle imaging measurements. The heterogeneous bimetallic shells were found to have a large scale of metal-enhanced emission relative to the monometallic or homogeneous bimetallic shells. It is because the heterogeneous bimetallic shells may display split dual plasmon resonances which can interact with the excitation and emission bands of the Ru(bpy)(3) (2+) complexes in the silica cores leading to more efficient near-field interactions. The prediction can be demonstrated by the lifetimes. Therefore, it is suggested that both the compositions and geometries of the metal shells can influence the interactions with the fluorophores in the cores. This observation also offers us an opportunity for developing plasmon-based fluorescence metal nanoparticles as novel nanoparticle imaging agents which have high performances in fluorescence cell or tissue imaging. PMID:23230456

  14. Cleaner water using bimetallic nanoparticle catalysts

    SciTech Connect

    Wong, Michael S.; Alvarez, Pedro J.J.; Fang, Yu-Iun; Akçin, Nurgül; Nutt, Michael O.; Miller, Jeffrey T.; Heck, Kimberly N.

    2010-10-22

    Groundwater contaminated by hazardous chlorinated compounds, especially chlorinated ethenes, continues to be a significant environmental problem in industrialized nations. The conventional treatment methods of activated carbon adsorption and air-stripping successfully remove these compounds by way of transferring them from the water phase into the solid or gas phase. Catalysis is a promising approach to remove chlorinated compounds completely from the environment, by converting them into safer, non-chlorinated compounds. Palladium-based materials have been shown to be very effective as hydrodechlorination catalysts for the removal of chlorinated ethenes and other related compounds. However, relatively low catalytic activity and a propensity for deactivation are significant issues that prevent their widespread use in groundwater remediation. Palladium-on-gold bimetallic nanoparticles, in contrast, were recently discovered to exhibit superior catalyst activity and improved deactivation resistance. This new type of material is a significant next-step in the development of a viable hydrodechlorination catalysis technology.

  15. Shaped Ir-Ni bimetallic nanoparticles for minimizing Ir utilization in oxygen evolution reaction.

    PubMed

    Lim, Jinkyu; Yang, Sungeun; Kim, Chanyeon; Roh, Chi-Woo; Kwon, Yongwoo; Kim, Yong-Tae; Lee, Hyunjoo

    2016-04-25

    Shaped Ir-Ni bimetallic nanoparticles were synthesized and used for electrocatalytic oxygen evolution reaction (OER). The obtained bimetallic nanoparticles showed significantly enhanced Ir mass activity and durability compared with Ir nanoparticles. PMID:27034092

  16. Gold over Branched Palladium Nanostructures for Photothermal Cancer Therapy.

    PubMed

    McGrath, Andrew J; Chien, Yi-Hsin; Cheong, Soshan; Herman, David A J; Watt, John; Henning, Anna M; Gloag, Lucy; Yeh, Chen-Sheng; Tilley, Richard D

    2015-12-22

    Bimetallic nanostructures show exciting potential as materials for effective photothermal hyperthermia therapy. We report the seed-mediated synthesis of palladium-gold (Pd-Au) nanostructures containing multiple gold nanocrystals on highly branched palladium seeds. The nanostructures were synthesized via the addition of a gold precursor to a palladium seed solution in the presence of oleylamine, which acts as both a reducing and a stabilizing agent. The interaction and the electronic coupling between gold nanocrystals and between palladium and gold broadened and red-shifted the localized surface plasmon resonance absorption maximum of the gold nanocrystals into the near-infrared region, to give enhanced suitability for photothermal hyperthermia therapy. Pd-Au heterostructures irradiated with an 808 nm laser light caused destruction of HeLa cancer cells in vitro, as well as complete destruction of tumor xenographs in mouse models in vivo for effective photothermal hyperthermia.

  17. Synthesis of Nanometer-Sized (bi)metallic Clusters with a Nuclear Reactor

    NASA Astrophysics Data System (ADS)

    Doudna, C. M.; Hund, J. F.; Bertino, M. F.

    Mono- and heteronuclear clusters were synthesized by irradiating with gamma rays from a nuclear reactor aqueous solutions containing ionic precursors. Ag, Au/Ag and Ag/Pd clusters were produced and characterized by optical absorption and transmission electron microscopy measurements. Electron diffraction measurements show that the clusters have a crystalline fcc structure. Ag and Au/Ag clusters have a lattice parameter which coincides with the bulk. In the case of Ag/Pd clusters, a homogeneous alloy is formed whose lattice parameter closely follows Vegard's law. The cluster size distribution is in the nanometer range, although coalescence processes lead often to large aggregates. Optical absorption spectra are in agreement with previously reported results, when the presence of large aggregates is taken into account.

  18. Thermal stability of bimetallic Au/Fe nanoparticles in silica matrix

    SciTech Connect

    Pannu, Compesh Singh, Udai B. Hooda, Sonu Kabiraj, D. Avasthi, D. K.

    2014-04-24

    Thin silica film containing Au and Fe bimetallic nanoparticles were prepared by atom beam cosputtering. The samples were annealed at different temperatures from 400 to 800° C to study the thermal stability of bimetallic nanoparticles using X ray diffraction. It is observed that at 800° C strong structural rearrangement took place leading to thermal decomposition of bimetallic nanoparticles.

  19. Degradation of chlorofluorocarbons using granular iron and bimetallic irons.

    PubMed

    Jeen, Sung-Wook; Lazar, Snezana; Gui, Lai; Gillham, Robert W

    2014-03-01

    Degradation of trichlorofluoromethane (CFC11) and 1,1,2-trichloro-1,2,2-trifluoroethane (CFC113) by granular iron and bimetallic (nickel- or palladium-enhanced) irons was studied in flow-through column tests. Both compounds were rapidly degraded, following pseudo-first-order kinetics with respect to the parent compounds. The average pseudo-first-order rate constants for CFC11 were similar among different materials, except for palladium-enhanced iron (PdFe), in which the rate of degradation was about two times faster than for the other materials. In the case of CFC113, the rate constants for bimetallic irons were about two to three times greater than for the regular iron material. The smaller than expected differences in degradation rate constants of chlorofluorocarbons (CFCs) between regular iron and bimetallic irons suggested little, if any, catalytic effect of the bimetallic materials in the initial degradation step. Subsequent degradation steps involved catalytic hydrogenation, however, playing a significant role in further degradation of reaction intermediates. The degradation intermediates and final products of CFC11 and CFC113 suggested that degradation proceeded through hydrogenolysis and α/β-elimination in the presence of regular iron (Fe) and nickel-enhanced iron (NiFe). Even though there is only minor benefit in the use of bimetallic iron in terms of degradation kinetics of the parent CFCs, enhanced degradation rates of intermediates such as chlorotriflouroethene (CTFE) in subsequent reaction steps could be beneficial. PMID:24492233

  20. Degradation of chlorofluorocarbons using granular iron and bimetallic irons.

    PubMed

    Jeen, Sung-Wook; Lazar, Snezana; Gui, Lai; Gillham, Robert W

    2014-03-01

    Degradation of trichlorofluoromethane (CFC11) and 1,1,2-trichloro-1,2,2-trifluoroethane (CFC113) by granular iron and bimetallic (nickel- or palladium-enhanced) irons was studied in flow-through column tests. Both compounds were rapidly degraded, following pseudo-first-order kinetics with respect to the parent compounds. The average pseudo-first-order rate constants for CFC11 were similar among different materials, except for palladium-enhanced iron (PdFe), in which the rate of degradation was about two times faster than for the other materials. In the case of CFC113, the rate constants for bimetallic irons were about two to three times greater than for the regular iron material. The smaller than expected differences in degradation rate constants of chlorofluorocarbons (CFCs) between regular iron and bimetallic irons suggested little, if any, catalytic effect of the bimetallic materials in the initial degradation step. Subsequent degradation steps involved catalytic hydrogenation, however, playing a significant role in further degradation of reaction intermediates. The degradation intermediates and final products of CFC11 and CFC113 suggested that degradation proceeded through hydrogenolysis and α/β-elimination in the presence of regular iron (Fe) and nickel-enhanced iron (NiFe). Even though there is only minor benefit in the use of bimetallic iron in terms of degradation kinetics of the parent CFCs, enhanced degradation rates of intermediates such as chlorotriflouroethene (CTFE) in subsequent reaction steps could be beneficial.

  1. Bimetallic Pt-Au nanocatalysts electrochemically deposited on graphene and their electrocatalytic characteristics towards oxygen reduction and methanol oxidation.

    PubMed

    Hu, Yaojuan; Zhang, Hua; Wu, Ping; Zhang, Hui; Zhou, Bo; Cai, Chenxin

    2011-03-01

    The burgeoning demand for clean and energy-efficient fuel cell system requires electrocatalysts to deliver greater activity and selectivity. Bimetallic catalysts have proven superior to single metal catalysts in this respect. This work reports the preparation, characterization, and electrocatalytic characteristics of a new bimetallic nanocatalyst. The catalyst, Pt-Au-graphene, was synthesized by electrodeposition of Pt-Au nanostructures on the surface of graphene sheets, and characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), and voltammetry. The morphology and composition of the nanocatalyst can be easily controlled by adjusting the molar ratio between Pt and Au precursors. The electrocatalytic characteristics of the nanocatalysts for the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) were systematically investigated by cyclic voltammetry. The Pt-Au-graphene catalysts exhibits higher catalytic activity than Au-graphene and Pt-graphene catalysts for both the ORR and the MOR, and the highest activity is obtained at a Pt/Au molar ratio of 2:1. Moreover, graphene can significantly enhance the long-term stability of the nanocatalyst toward the MOR by effectively removing the accumulated carbonaceous species formed in the oxidation of methanol from the surface of the catalyst. Therefore, this work has demonstrated that a higher performance of ORR and the MOR could be realized at the Pt-Au-graphene electrocatalyst while Pt utilization also could be greatly diminished. This method may open a general approach for the morphology-controlled synthesis of bimetallic Pt-M nanocatalysts, which can be expected to have promising applications in fuel cells. PMID:21229152

  2. Bimetallic strip for low temperature use

    DOEpatents

    Bussiere, Jean F.; Welch, David O.; Suenaga, Masaki

    1981-01-01

    There is provided a class of mechanically pre-stressed structures, suitably bi-layer strips comprising a layer of group 5 transition metals in intimate contact with a layer of an intermetallic compound of said transition metals with certain group 3A, 4A or 5A metals or metalloids suitably gallium, indium, silicon, germanium, tin, arsenic or antimony. The changes of Young's modulus of these bi-layered combinations at temperatures in the region of but somewhat above absolute zero provides a useful means of sensing temperature changes. Such bi-metallic strips may be used as control strips in thermostats, in direct dial reading instruments, or the like. The structures are made by preparing a sandwich of a group 5B transition metal strip between the substantially thicker strips of an alloy between copper and a predetermined group 3A, 4A or 5A metal or metalloid, holding the three layers of the sandwich in intimate contact heating the same, cooling the same and removing the copper alloy and then removing one of the two thus formed interlayer alloys between said transition metal and the metal previously alloyed with copper.

  3. Structure-Property Relationship in Metal Carbides and Bimetallic Alloys

    SciTech Connect

    Chen, Jingguan

    2014-03-04

    The primary objective of our DOE/BES sponsored research is to use carbide and bimetallic catalysts as model systems to demonstrate the feasibility of tuning the catalytic activity, selectivity and stability. Our efforts involve three parallel approaches, with the aim at studying single crystal model surfaces and bridging the “materials gap” and “pressure gap” between fundamental surface science studies and real world catalysis. The utilization of the three parallel approaches has led to the discovery of many intriguing catalytic properties of carbide and bimetallic surfaces and catalysts. During the past funding period we have utilized these combined research approaches to explore the possibility of predicting and verifying bimetallic and carbide combinations with enhanced catalytic activity, selectivity and stability.

  4. Plasmon-mediated syntheses of metallic nanostructures.

    PubMed

    Langille, Mark R; Personick, Michelle L; Mirkin, Chad A

    2013-12-23

    The ability to prepare noble metal nanostructures of a desired composition, size, and shape enables their resulting properties to be exquisitely tailored, which has led to the use of these structures in numerous applications, ranging from medicine to electronics. The prospect of using light to guide nanoparticle reactions is extremely attractive since one can, in principle, regulate particle growth based on the ability of the nanostructures to absorb a specific excitation wavelength. Therefore, using the nature of light, one can generate a homogenous population of product nanoparticles from a heterogeneous starting population. The best example of this is afforded by plasmon-mediated syntheses of metal nanoparticles, which use visible light irradiation and plasmon excitation to drive the chemical reduction of Ag(+) by citrate. Since the initial discovery that Ag triangular prisms could be prepared by the photo-induced conversion of Ag spherical nanoparticles, plasmon-mediated synthesis has become a highly controllable technique for preparing a number of different Ag particles with tight control over shape, as well as a wide variety of Au-Ag bimetallic nanostructures. We discuss the underlying physical and chemical factors that drive structural selection and conclude by outlining some of the important design considerations for controlling particle shape as learned through studies of plasmon-mediated reactions, but applicable to all methods of noble metal nanocrystal synthesis.

  5. METALLIC AND HYBRID NANOSTRUCTURES: FUNDAMENTALS AND APPLICATIONS

    SciTech Connect

    Murph, S.

    2012-05-02

    This book chapter presents an overview of research conducted in our laboratory on preparation, optical and physico-chemical properties of metallic and nanohybrid materials. Metallic nanoparticles, particularly gold, silver, platinum or a combination of those are the main focus of this review manuscript. These metallic nanoparticles were further functionalized and used as templates for creation of complex and ordered nanomaterials with tailored and tunable structural, optical, catalytic and surface properties. Controlling the surface chemistry on/off metallic nanoparticles allows production of advanced nanoarchitectures. This includes coupled or encapsulated core-shell geometries, nano-peapods, solid or hollow, monometallic/bimetallic, hybrid nanoparticles. Rational assemblies of these nanostructures into one-, two- and tridimensional nano-architectures is described and analyzed. Their sensing, environmental and energy related applications are reviewed.

  6. Bimetallic alloy electrocatalysts with multilayered platinum-skin surfaces

    DOEpatents

    Stamenkovic, Vojislav R.; Wang, Chao; Markovic, Nenad M.

    2016-01-26

    Compositions and methods of preparing a bimetallic alloy having enhanced electrocatalytic properties are provided. The composition comprises a PtNi substrate having a surface layer, a near-surface layer, and an inner layer, where the surface layer comprises a nickel-depleted composition, such that the surface layer comprises a platinum skin having at least one atomic layer of platinum.

  7. Self-discharge in bimetallic cells containing alkali metal

    NASA Technical Reports Server (NTRS)

    Foster, M. S.; Hesson, J. C.; Shimotake, H.

    1969-01-01

    Theoretical analysis of thermally regenerative bimetallic cells with alkali metal anodes shows a relation between the current drawn and the rate of discharge under open-circuit conditions. The self-discharge rate of the cell is due to the dissolution and ionization of alkali metal atoms in the fused-salt electrolyte

  8. Spectroscopic Elucidation of First Steps of Supported Bimetallic Cluster Formation

    SciTech Connect

    Kulkarni, A.; Gates, B.C.

    2009-12-23

    Initial steps of bimetallic Ru-Os cluster formation on MgO in the presence of H{sub 2} are analyzed by EXAFS and IR spectroscopy. Ru-Os bond formation takes place after decarbonylation of Ru{sub 3} clusters and subsequently, at higher temperatures, of Os{sub 3} clusters to generate coordinative unsaturation.

  9. Lithium-tellurium bimetallic cell has increased voltage

    NASA Technical Reports Server (NTRS)

    Cairns, E. J.; Rogers, G. L.; Shimotake, H.

    1968-01-01

    Lithium-tellurium secondary cell with a fused lithium halide electrolyte, tested in the temperature range 467 degrees to 500 degrees C, showed improvement over the sodium bismuth cell. The voltage of this bimetallic cell was increased by using the more electropositive anode material, lithium, and the more electronegative cathode material, tellurium.

  10. Nickel Cobaltite Nanostructures for Photoelectric and Catalytic Applications.

    PubMed

    Liu, Shaoxiong; Hu, Linfeng; Xu, Xiaojie; Al-Ghamdi, Ahmed A; Fang, Xiaosheng

    2015-09-01

    Bimetallic oxide nickel cobaltite (NiCo2 O4 ) shows extensive potential for innovative photoelectronic and energetic materials owing to their distinctive physical and chemical properties. In this review, representative fabrications and applications of NiCo2 O4 nanostructures are outlined for photoelectronic conversion, catalysis, and energy storage, aiming to promote the development of NiCo2 O4 nanomaterials in these fields through an analysis and comparison of their diverse nanostructures. Firstly, a brief introduction of the spinel structures, properties, and morphologies of NiCo2 O4 nanomaterials are presented. Then, the advanced progress of NiCo2 O4 nanomaterials for both photoelectronic conversion and energy fields is summarized including such examples as solar cells, electrocatalysis, and lithium ion batteries. Finally, further prospects and promising developments of NiCo2 O4 nanomaterials in these significant fields are proposed.

  11. Nickel Cobaltite Nanostructures for Photoelectric and Catalytic Applications.

    PubMed

    Liu, Shaoxiong; Hu, Linfeng; Xu, Xiaojie; Al-Ghamdi, Ahmed A; Fang, Xiaosheng

    2015-09-01

    Bimetallic oxide nickel cobaltite (NiCo2 O4 ) shows extensive potential for innovative photoelectronic and energetic materials owing to their distinctive physical and chemical properties. In this review, representative fabrications and applications of NiCo2 O4 nanostructures are outlined for photoelectronic conversion, catalysis, and energy storage, aiming to promote the development of NiCo2 O4 nanomaterials in these fields through an analysis and comparison of their diverse nanostructures. Firstly, a brief introduction of the spinel structures, properties, and morphologies of NiCo2 O4 nanomaterials are presented. Then, the advanced progress of NiCo2 O4 nanomaterials for both photoelectronic conversion and energy fields is summarized including such examples as solar cells, electrocatalysis, and lithium ion batteries. Finally, further prospects and promising developments of NiCo2 O4 nanomaterials in these significant fields are proposed. PMID:26121217

  12. Structural analysis of palladium-decorated gold nanoparticles as colloidal bimetallic catalysts.

    SciTech Connect

    Fang, Y. L.; Miller, J. T.; Guo, N.; Heck, K. N.; Alvarez, P. J. J.; Wong, M. S.

    2011-02-02

    Bimetallic palladium-decorated gold nanoparticle (Pd/Au NP) catalysts are significantly more active than palladium-only catalysts, but the mechanism for enhancement is not completely clear for most reactions, like the aqueous-phase hydrodechlorination of trichloroethene. In this study, we conducted X-ray absorption spectroscopy on carbon-supported Pd/Au NPs to obtain information about the local atomic environment (i.e., oxidation states, coordination numbers, and bond distances) of the two metals under different treatment conditions. The as-synthesized NPs were confirmed to have a Pd-shell/Au-core nanostructure, in which the Pd was found as surface ensembles. Upon exposure to room temperature in air, a portion of the Pd, but not the Au, was oxidized. In comparison, nearly the entire surface of monometallic Pd NPs was oxidized, suggesting that Au in Pd/Au NPs imparts oxidation resistance to Pd atoms. The surface Pd was found randomly distributed, presumably as a PdAu surface alloy, after reduction at 300 C. X-ray absorption spectroscopy provides direct evidence for the Pd-shell/Au-core structure of Pd/Au NPs, and suggests that metallic Pd in the Pd/Au NPs is a source for higher catalytic activity for aqueous-phase trichloroethene hydrodechlorination.

  13. Enhanced and tunable optical quantum efficiencies from plasmon bandwidth engineering in bimetallic CoAg nanoparticles

    NASA Astrophysics Data System (ADS)

    Malasi, A.; Taz, H.; Ehrsam, M.; Goodwin, J.; Garcia, H.; Kalyanaraman, R.

    2016-10-01

    Plasmonic nanoparticles are amongst the most effective ways to resonantly couple optical energy into and out of nanometer sized volumes. However, controlling and/or tuning the transfer of this incident energy to the surrounding near and far field is one of the most interesting challenges in this area. Due to the dielectric properties of metallic silver (Ag), its nanoparticles have amongst the highest radiative quantum efficiencies (η), i.e., the ability to radiatively transfer the incident energy to the surrounding. Here we report the discovery that bimetallic nanoparticles of Ag made with immiscible and plasmonically weak Co metal can show comparable and/or even higher η values. The enhancement is a result of the narrowing of the plasmon bandwidth from these bimetal systems. The phenomenological explanation of this effect based on the dipolar approximation points to the reduction in radiative losses within the Ag nanoparticles when in contact with cobalt. This is also supported by a model of coupling between poor and good conductors based on the surface to volume ratio. This study presents a new type of bandwidth engineering, one based on using bimetal nanostructures, to tune and/or enhance the quality factor and quantum efficiency for near and far-field plasmonic applications.

  14. Bimetallic dendrimer-encapsulated nanoparticles as catalysts: a review of the research advances

    PubMed Central

    Rempel, Garry L.

    2008-01-01

    Bimetallic dendrimer-encapsulated nanoparticles (DENs) are important materials, because they have demonstrated improvement in performance compared to the monometallic DENs in many systems when they are used as catalysts. This tutorial review focuses on the recent research advances in bimetallic DENs with respect to their synthesis, characterization, and applications as catalysts. Bimetallic DENs can be made mainly via three routes: co-complexation, sequential loading, and partial displacement. The research in bimetallic DENs has been significantly promoted by the advancement of characterization instruments. The performances of bimetallic DENs as homogeneous and heterogeneous catalysts in organic synthesis have been compared with both monometallic DENs and their physical mixtures. It is concluded that the synergistic electronic effect in bimetallic nanoparticles enhances their catalytic activities. PMID:18648686

  15. Nanostructured photovoltaics

    NASA Astrophysics Data System (ADS)

    Fu, Lan; Tan, H. Hoe; Jagadish, Chennupati

    2013-01-01

    Energy and the environment are two of the most important global issues that we currently face. The development of clean and sustainable energy resources is essential to reduce greenhouse gas emission and meet our ever-increasing demand for energy. Over the last decade photovoltaics, as one of the leading technologies to meet these challenges, has seen a continuous increase in research, development and investment. Meanwhile, nanotechnology, which is considered to be the technology of the future, is gradually revolutionizing our everyday life through adaptation and incorporation into many traditional technologies, particularly energy-related technologies, such as photovoltaics. While the record for the highest efficiency is firmly held by multijunction III-V solar cells, there has never been a shortage of new research effort put into improving the efficiencies of all types of solar cells and making them more cost effective. In particular, there have been extensive and exciting developments in employing nanostructures; features with different low dimensionalities, such as quantum wells, nanowires, nanotubes, nanoparticles and quantum dots, have been incorporated into existing photovoltaic technologies to enhance their performance and/or reduce their cost. Investigations into light trapping using plasmonic nanostructures to effectively increase light absorption in various solar cells are also being rigorously pursued. In addition, nanotechnology provides researchers with great opportunities to explore the new ideas and physics offered by nanostructures to implement advanced solar cell concepts such as hot carrier, multi-exciton and intermediate band solar cells. This special issue of Journal of Physics D: Applied Physics contains selected papers on nanostructured photovoltaics written by researchers in their respective fields of expertise. These papers capture the current excitement, as well as addressing some open questions in the field, covering topics including the

  16. Structural Characterization of Bimetallic Nanocrystal Electrocatalysts

    SciTech Connect

    Cullen, David A

    2016-01-01

    Late transition metal nanocrystals find applications in heterogeneous catalysis such as plasmon-enhanced catalysis and as electrode materials for fuel cells, a zero-emission and sustainable energy technology. Their commercial viability for automotive transportation has steadily increased in recent years, almost exclusively due to the discovery of more efficient bimetallic nanocatalysts for the oxygen reduction reaction (ORR) at the cathode. Despite improvements to catalyst design, achieving high activity while maintaining durability is essential to further enhance their performance for this and other important applications in catalysis. Electronic effects arising from the generation of metal-metal interfaces, from plasmonic metals, and from lattice distortions, can vastly improve sorption properties at catalytic surfaces, while increasing durability.[1] Multimetallic lattice-strained nanoparticles are thus an interesting opportunity for fundamental research.[2,3] A colloidal synthesis approach is demonstrated to produce AuPd alloy and Pd@Au core-shell nanoicosahedra as catalysts for electro-oxidations. The nanoparticles are characterized using aberration-corrected scanning transmission electron microscopy (ac-STEM) and large solid angle energy dispersive X-ray spectroscopy (EDS) on an FEI Talos 4-detector STEM/EDS system. Figure 1 shows bright-field (BF) and high-angle annular dark-field (HAADF) ac-STEM images of the alloy and core-shell nanoicosahedra together with EDS line-scans and elemental maps. These structures are unique in that the presence of twin boundaries, alloying, and core-shell morphology could create highly strained surfaces and interfaces. The shell thickness of the core-shell structures observed in HAADF-STEM images is tuned by adjusting the ratio between metal precursors (Figure 2a-f) to produce shells ranging from a few to several monolayers. Specific activity was measured in ethanol electro-oxidation to examine the effect of shell thickness on

  17. Nanosegregated bimetallic oxide anode catalyst for proton exchange membrane electrolyzer

    DOEpatents

    Danilovic, Nemanja; Kang, Yijin; Markovic, Nenad; Stamenkovic, Vojislav; Myers, Deborah J.; Subbaraman, Ram

    2016-08-23

    A surface segregated bimetallic composition of the formula Ru.sub.1-xIr.sub.x wherein 0.1.ltoreq.x.ltoreq.0.75, wherein a surface of the material has an Ir concentration that is greater than an Ir concentration of the material as a whole is provided. The surface segregated material may be produced by a method including heating a bimetallic composition of the formula Ru.sub.1-xIr.sub.x, wherein 0.1.ltoreq.x.ltoreq.0.75, at a first temperature in a reducing environment, and heating the composition at a second temperature in an oxidizing environment. The surface segregated material may be utilized in electrochemical devices.

  18. Bimetallic Wiregauze Supported Pt-Ru Nanocatalysts for Hydrogen Mitigation.

    PubMed

    Sanap, Kiran K; Varma, S; Waghmode, S B; Sharma, P; Manoj, N; Vatsa, R K; Bharadwaj, S R

    2015-05-01

    Passive autocatalytic recombiner (PAR) is one of the most suitable devices for mitigation of hydrogen, generated in nuclear power plant under accidental conditions. For this purpose we report development of stainless steel wire gauze supported Pt-Ru nanoparticles as catalysts. Simultaneous electroless deposition has been employed for the synthesis of the catalysts. Pt-Ru based bimetallic catalysts were characterized for their rate of coating kinetics, noble metal loading, phase purity by XRD and surface morphology by SEM, TEM and elemental analysis by SIMS. Developed catalysts were found to be active for efficient recombination of hydrogen and oxygen in air as well as in presence of various prospective poisons like CO2, CH4, CO and relative humidity. Pt-Ru based bimetallic catalyst with 0.9% loading was found to be active for CO poisoning up to 400 ppm of CO. PMID:26504972

  19. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction

    SciTech Connect

    Song, Chunshan; Schobert, H.H.

    1993-02-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

  20. Centrifugally cast bimetallic pipe for offshore corrosion resistant pipelines

    SciTech Connect

    Yoshitake, A.; Torigoe, T.

    1994-12-31

    Centrifugally cast bimetallic pipes and fittings have been developed for the use of offshore oil and gas production. The metallurgical properties, mechanical properties, and corrosion properties of centrifugal a cast bimetallic pipe with outside metal of API 5L X52 to X65 internally clad with alloy 825 and 625 are discussed. First, molten steel for outer pipe is introduced into a rotating metallic mold. During the solidification of the outer pipe (carbon steel), the temperature of the pipe inside is monitored. After the solidification of the outer pipe, and when a certain temperature is reached, then a corrosion resistant alloy such as Alloy 825 or 625 for inside layer is poured. By controlling the casting conditions and selecting suitable flux, sound metallurgical bonded bimetallic pipe is produced with a minimum mixing layer at the interface also keeping a homogeneous outside wall thickness along the pipe length. The weld joints of the pipe are also evaluated from the view points of weldability, mechanical strength, fracture toughness, and corrosion resistance properties. The welding method applied was basically TIG welding (GTAW). COD tests at {minus}10 C are applied to the welds to investigate fracture toughness of the weld joints. Huey test according to ASTM A262C is carried out on the root of the welds as the corrosion test. As a result, the weld joint using filler wire of alloy625 from root to cover pass has proved a very reliable method from the point of view of mechanical and corrosion resistance properties. These centrifugally cast bimetallic pipes and fittings have been widely used for riser pipes, template process lines, top side and subsea manifolds, and flow bends for christmas trees in the North Sea.

  1. Bimetallic catalysts for upgrading of biomass to fuels and chemicals.

    PubMed

    Alonso, David Martin; Wettstein, Stephanie G; Dumesic, James A

    2012-12-21

    Research interest in biomass conversion to fuels and chemicals has increased significantly in the last decade as the necessity for a renewable source of carbon has become more evident. Accordingly, many different reactions and processes to convert biomass into high-value products and fuels have been proposed in the literature. Special attention has been given to the conversion of lignocellulosic biomass, which does not compete with food sources and is widely available as a low cost feedstock. In this review, we start with a brief introduction on lignocellulose and the different chemical structures of its components: cellulose, hemicellulose, and lignin. These three components allow for the production of different chemicals after fractionation. After a brief overview of the main reactions involved in biomass conversion, we focus on those where bimetallic catalysts are playing an important role. Although the reactions are similar for cellulose and hemicellulose, which contain C(6) and C(5) sugars, respectively, different products are obtained, and therefore, they have been reviewed separately. The third major fraction of lignocellulose that we address is lignin, which has significant challenges to overcome, as its structure makes catalytic processing more challenging. Bimetallic catalysts offer the possibility of enabling lignocellulosic processing to become a larger part of the biofuels and renewable chemical industry. This review summarizes recent results published in the literature for biomass upgrading reactions using bimetallic catalysts. PMID:22872312

  2. Antibacterial activity of graphene supported FeAg bimetallic nanocomposites.

    PubMed

    Ahmad, Ayyaz; Qureshi, Abdul Sattar; Li, Li; Bao, Jie; Jia, Xin; Xu, Yisheng; Guo, Xuhong

    2016-07-01

    We report the simple one pot synthesis of iron-silver (FeAg) bimetallic nanoparticles with different compositions on graphene support. The nanoparticles are well dispersed on the graphene sheet as revealed by the TEM, XRD, and Raman spectra. The antibacterial activity of graphene-FeAg nanocomposite (NC) towards Bacillus subtilis, Escherichia coli, and Staphylococcus aureus was investigated by colony counting method. Graphene-FeAg NC demonstrates excellent antibacterial activity as compared to FeAg bimetallic without graphene. To understand the antibacterial mechanism of the NC, oxidative stress caused by reactive oxygen species (ROS) and the glutathione (GSH) oxidation were investigated in the system. It has been observed that ROS production and GSH oxidation are concentration dependent while the increase in silver content up to 50% generally enhances the ROS production while ROS decreases on further increase in silver content. Graphene loaded FeAg NC demonstrates higher GSH oxidation capacity than bare FeAg bimetallic nanocomposite. The mechanism study suggests that the antibacterial activity is probably due to membrane and oxidative stress produced by the nanocomposites. The possible antibacterial pathway mainly includes the non-ROS oxidative stress (GSH oxidation) while ROS play minor role. PMID:27038914

  3. Synthesis and characterization of Ni-Au bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Nik Roselina, N. R.; Azizan, A.; Hyie, Koay Mei; Murad, Mardziah Che; Abdullah, Abdul Hakim

    2015-04-01

    Bimetallic structure of nanoparticles is of great interest due to their extraordinary properties, especially in combining the specialty of the core and its shell. This work reports the effect of pH on the synthesis of Ni-Au (nickel-gold) bimetallic nanoparticles. The synthesis involves a two-step process where Ni nanoparticles were first synthesized using polyol method with hydrazine as the reducing agent. This was followed by the process of reducing AuCl4- to Au in the solution containing pre-prepared Ni to form Ni-Au bimetallic nanoparticles using sodium citrate as the reducing agent. The results obtained from Transmission Electron Microscopy (TEM) show that the process can possibly produce either core-shell structure, or mixture of Ni and Au nanoparticles. Magnetic property of core-shell structure investigated using Vibrating Sample Magnetometer (VSM) demonstrated typical characteristic of ferromagnetic with an increased magnetization as compared to Ni nanoparticles. The saturation magnetization (Ms) and coercivity (Hc) were obtained as 19.1 emu/g and 222.3 Oe, respectively.

  4. Enhanced dehalogenation of halogenated methanes by bimetallic Cu/Al.

    PubMed

    Lien, Hsing-Lung; Zhang, Weixian

    2002-10-01

    A low-cost and high effective copper/aluminum (Cu/Al) bimetal has been developed for treatments of halogenated methanes, including dichloromethane, in near neutral and high pH aqueous systems. Bimetallic Cu/Al was prepared by a simple two-step synthetic method where Cu was deposited onto the Al surface. The presence of Cu on Al significantly enhanced rates of degradation of halogenated methanes and reduced toxic halogenated intermediates. The stability of Cu/Al was preliminarily studied by a multi-spiking batch experiment where complete degradation of carbon tetrachloride was achieved for seven times although the Cu/Al aging was found. Roles of Cu may involve protecting Al against an undesirable oxidation with water, enhancing reaction rates through the galvanic corrosion, and increasing the selectivity to a benign compound (i.e., methane). Kinetic analyses indicated that the activity of bimetallic Cu/Al was comparable to that of iron-based bimetals (e.g., palladized iron) and zero-valent metals. Bimetallic Cu/Al could be a promising reactive reagent for remediation of halogenated solvents-contaminated groundwater associated with high pH problems.

  5. Surface-enhanced Raman scattering (SERS)-based volatile organic compounds (VOCs) detection using plasmonic bimetallic nanogap substrate

    NASA Astrophysics Data System (ADS)

    Wong, Chi Lok; Dinish, U. S.; Buddharaju, Kavitha Devi; Schmidt, Michael Stenbæk; Olivo, Malini

    2014-08-01

    In this paper, we present surface-enhanced Raman scattering (SERS)-based volatile organic compounds (VOCs) detection with bimetallic nanogap structure substrate. Deep UV photolithography at the wavelength of 250 nm is used to pattern circular shape nanostructures. The nanogap between adjacent circular patterns is 30 ± 5 nm. Silver (30 nm) and gold (15 nm) plasmonic active layers are deposited on the nanostructures subsequently. SERS measurements on different concentrations of acetone vapor ranged from 0.7, 1.5, 3.5, 10.3, 24.5 % and control have been performed with the substrate. The measurement results are found reproducible, and the detection limit is found to be 9.5 pg (acetone molecule). The detection sensitivity is 28.7 % higher than that of the recent reported leaning silicon nanopillar substrate. With further system miniaturization, the sensing technique can work as a portable SERS-based VOCs detection platform for point-of-care breath analysis, homeland security, chemical sensing and environmental monitoring.

  6. NOVEL METALLIC AND BIMETALLIC CROSS-LINKED POLY (VINYL ALCOHOL) NANOCOMPOSITES PREPARED UNDER MICROWAVE IRRADIATION

    EPA Science Inventory

    A facile microwave irradiation approach that results in a cross-linking reaction of poly (vinyl alcohol) (PVA) with metallic and bimetallic systems is described. Nanocomposites of PVA cross-linked metallic systems such as Pt, Cu, and In and bimetallic systems such as Pt-In, Ag-P...

  7. PREPARATION OF NOVEL METALLIC AND BIMETALLIC CROSS-LINKED POLY (VINYL ALCOHOL) NANOCOMPOSITES UNDER MICROWAVE IRRADIATION

    EPA Science Inventory

    A facile method utilizing microwave irradiation is described that accomplishes the cross-linking reaction of PVA with metallic and bimetallic systems. Nanocomposites of PVA-cross-linked metallic systems such as Pt, Cu, and In and bimetallic systems such as Pt-In, Ag-Pt, Pt-Fe, Cu...

  8. Novel of core-shell AlOOH/Cu nanostructures: Synthesis, characterization, antimicrobial activity and in vitro toxicity in Neuro-2a cells

    NASA Astrophysics Data System (ADS)

    Bakina, O. V.; Fomenko, A. N.; Korovin, M. S.; Glazkova, E. A.; Svarovskaya, N. V.

    2016-08-01

    Core-shell micro/nanostructures were fabricated by the reaction of Al/Cu bimetallic nanoparticles with water. Al/Cu nanoparticles have been obtained using the method of simultaneous electrical explosion of a pair of the corresponding metal wires in an argon atmosphere. The nanoparticles are chemically active and interact with water at 60°C to form core-shell micro/nanostructures. The obtained products were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and dynamic light scattering and the nitrogen adsorption method. The antibacterial activity of the synthesized structures was investigated against E. coli and St. aureus. The toxic effect of these nanostructures against the Neuro-2a neuroblastoma cell line was investigated. AlOOH/Cu nanostructures are shown to inhibit cell proliferation. The AlOOH/Cu nanostructures are good candidates for medical applications.

  9. Cleave and capture chemistry illustrated through bimetallic-induced fragmentation of tetrahydrofuran

    NASA Astrophysics Data System (ADS)

    Mulvey, Robert E.; Blair, Victoria L.; Clegg, William; Kennedy, Alan R.; Klett, Jan; Russo, Luca

    2010-07-01

    The cleavage of ethers is commonly encountered in organometallic chemistry, although rarely studied in the context of new, emerging bimetallic reagents. Recently, it was reported that a bimetallic sodium-zinc base can deprotonate cyclic tetrahydrofuran under mild conditions without opening its heterocyclic (OC4) ring. In marked contrast to this synergic sedation, herein we show that switching to the more reactive sodium-magnesium or sodium-manganese bases promotes cleavage of at least six bonds in tetrahydrofuran, but uniquely the ring fragments are captured in separate crystalline complexes. Oxide fragments occupy guest positions in bimetallic, inverse crown ethers and C4 fragments ultimately appear in bimetallated butadiene molecules. These results demonstrate the special synergic reactivity that can be executed by bimetallic reagents, which include the ability to capture and control, and thereby study, reactive fragments from sensitive substrates.

  10. Cleave and capture chemistry illustrated through bimetallic-induced fragmentation of tetrahydrofuran.

    PubMed

    Mulvey, Robert E; Blair, Victoria L; Clegg, William; Kennedy, Alan R; Klett, Jan; Russo, Luca

    2010-07-01

    The cleavage of ethers is commonly encountered in organometallic chemistry, although rarely studied in the context of new, emerging bimetallic reagents. Recently, it was reported that a bimetallic sodium-zinc base can deprotonate cyclic tetrahydrofuran under mild conditions without opening its heterocyclic (OC(4)) ring. In marked contrast to this synergic sedation, herein we show that switching to the more reactive sodium-magnesium or sodium-manganese bases promotes cleavage of at least six bonds in tetrahydrofuran, but uniquely the ring fragments are captured in separate crystalline complexes. Oxide fragments occupy guest positions in bimetallic, inverse crown ethers and C(4) fragments ultimately appear in bimetallated butadiene molecules. These results demonstrate the special synergic reactivity that can be executed by bimetallic reagents, which include the ability to capture and control, and thereby study, reactive fragments from sensitive substrates. PMID:20571579

  11. Bimetallic ruthenium-copper nanoparticles embedded in mesoporous carbon as an effective hydrogenation catalyst.

    PubMed

    Liu, Jiajia; Zhang, Li Li; Zhang, Jiatao; Liu, Tao; Zhao, X S

    2013-11-21

    Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in D-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal. PMID:24072134

  12. Bimetallic ruthenium-copper nanoparticles embedded in mesoporous carbon as an effective hydrogenation catalyst

    NASA Astrophysics Data System (ADS)

    Liu, Jiajia; Zhang, Li Li; Zhang, Jiatao; Liu, Tao; Zhao, X. S.

    2013-10-01

    Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in d-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal.Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in d-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03813k

  13. An in-depth understanding of the bimetallic effects and coked carbon species on an active bimetallic Ni(Co)/Al2O3 dry reforming catalyst.

    PubMed

    Liao, Xin; Gerdts, Rihards; Parker, Stewart F; Chi, Lina; Zhao, Yongxiang; Hill, Martyn; Guo, Junqiu; Jones, Martin O; Jiang, Zheng

    2016-06-29

    Ni/Al2O3, Co/Al2O3 and bimetallic Ni(Co)/Al2O3 catalysts were prepared using an impregnation method and employed in CO2 dry reforming of methane under coking-favored conditions. The spent catalysts were carefully characterized using typical characterization technologies and inelastic neutron scattering spectroscopy. The bimetallic catalyst exhibited a superior activity and anti-coking performance compared to Ni/Al2O3, while the most resistant to coking behavior was Co/Al2O3. The enhanced activity of the Ni(Co)/Al2O3 bimetallic catalyst is attributed to the reduced particle size of metallic species and resistance to forming stable filamentous carbon. The overall carbon deposition on the spent bimetallic catalyst is comparable to that of the spent Ni/Al2O3 catalyst, whereas the carbon deposited on the bimetallic catalyst is mainly less-stable carbonaceous species as confirmed by SEM, TPO, Raman and INS characterization. This study provides an in depth understanding of alloy effects in catalysts, the chemical nature of coked carbon on spent Ni-based catalysts and, hopefully, inspires the creative design of a new bimetallic catalyst for dry reforming reactions. PMID:27326792

  14. An in-depth understanding of the bimetallic effects and coked carbon species on an active bimetallic Ni(Co)/Al2O3 dry reforming catalyst.

    PubMed

    Liao, Xin; Gerdts, Rihards; Parker, Stewart F; Chi, Lina; Zhao, Yongxiang; Hill, Martyn; Guo, Junqiu; Jones, Martin O; Jiang, Zheng

    2016-06-29

    Ni/Al2O3, Co/Al2O3 and bimetallic Ni(Co)/Al2O3 catalysts were prepared using an impregnation method and employed in CO2 dry reforming of methane under coking-favored conditions. The spent catalysts were carefully characterized using typical characterization technologies and inelastic neutron scattering spectroscopy. The bimetallic catalyst exhibited a superior activity and anti-coking performance compared to Ni/Al2O3, while the most resistant to coking behavior was Co/Al2O3. The enhanced activity of the Ni(Co)/Al2O3 bimetallic catalyst is attributed to the reduced particle size of metallic species and resistance to forming stable filamentous carbon. The overall carbon deposition on the spent bimetallic catalyst is comparable to that of the spent Ni/Al2O3 catalyst, whereas the carbon deposited on the bimetallic catalyst is mainly less-stable carbonaceous species as confirmed by SEM, TPO, Raman and INS characterization. This study provides an in depth understanding of alloy effects in catalysts, the chemical nature of coked carbon on spent Ni-based catalysts and, hopefully, inspires the creative design of a new bimetallic catalyst for dry reforming reactions.

  15. Transition metal bimetallic oxycarbides: Synthesis, characterization, and activity studies

    SciTech Connect

    Oyama, S.T.; Yu, C.C.; Ramanathan, S.

    1999-06-10

    A new family of bimetallic oxycarbide compounds M{sup I}-M{sup II}-O-C (M{sup I} = Mo, W; M{sup II} = V, Nb, Cr, Fe, Co, Ni) has been synthesized by carburizing bimetallic oxide precursors using a temperature-programmed method. The oxide precursors are prepared by conventional solid-state reaction between two appropriate monometallic oxides. The synthesis involves passing a 20 mol% CH{sub 4} in H{sub 2} mixture over the oxide precursors while raising the temperature at a linear rate of 8.3 {times} 10{sup {minus}2} K/s (5 K/min) to a final temperature (T{sub max}) which is held for a period of time (t{sub hold}). The synthesis, chemisorption properties, and reactivation of the materials indicate that the compounds can be divided into two groups of different reducibility (high and low). Their surface activity and surface area are evaluated based on CO chemisorption and N{sub 2} physisorption measurements. It is found that the CO number density correlates with the reducibility of the compounds. The catalysts were evaluated for hydroprocessing in a three-phase trickle-bed reactor operated at 3.1 MPa and 643 K. The feed was a model liquid mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt% aromatics (tetralin), and balance aliphatics (tetradecane). The bimetallic oxycarbides had moderate activity for HDN of quinoline, with Nb-Mo-O-C showing higher HDN than a commercial sulfided Ni-Mo/Al{sub 2}O{sub 3} catalyst tested at the same conditions. X-ray diffraction of the spent catalysts indicated that the oxycarbides of the early transition metals were tolerant of sulfur, while those involving the late transition metals showed bulk sulfide phases.

  16. Exploration of Nanotube Structure Selectivity Using Bimetallic Catalysts

    NASA Astrophysics Data System (ADS)

    Pfefferle, Lisa

    2007-10-01

    Achieving selectivity for nanotube chirality is one of the holy grails for single-walled carbon nanotube research. One approach we are following is based on the ability to engineer the size and state of the initiating metal particle to constrain the type of cap formed. The chirality/structure of a nanotube is controlled by carbon cap formation on the metal particle during the nucleation step. It has been proposed that varying the carbon-metal catalyst binding energy could help lead to structure selectivity. One reason theoretically proposed for the favoring of armchair nanotubes, for example, is the proximity of low energy binding locations for two carbon atoms. Thus blocking sites or perturbing the binding energy on adjacent sites could in theory affect the structure of the carbon cap formed in the nucleation step. Our goal is to demonstrate structure selectivity in the growth of single wall carbon nanotubes (SWNT) using a bimetallic catalyst. The catalyst used was a bimetallic CoCr-MCM 41 and the effect of different molecular ratios between the two metals on the SWNT diameter distribution was studied. We have found that by adding Cr to the Co-MCM 41 monometallic catalyst the diameter distribution shifted in a systematic manner correlated to the development of a bimetallic phase as characterized by X-Ray absorption spectroscopy (XAS). We have also found that the shift is accompanied by suppression of metallic SWNT, particularly those with diameter over 0.9 nm. We are also currently exploring the possibility of a further narrowing of the distribution by lowering the reaction temperatures.

  17. Structural characterization of bimetallic Pd-Cu vapor derived catalysts

    NASA Astrophysics Data System (ADS)

    Balerna, Antonella; Evangelisti, Claudio; Psaro, Rinaldo; Fusini, Graziano; Carpita, Adriano

    2016-05-01

    Pd-Cu bimetallic Solvated Metal Atoms (SMA) were synthesized by metal vapor synthesis technique and supported on PVPy resin. Since the catalytic activity, of the Pd-Cu system turned out to be quite high also compared to the corresponding monometallic system, a structural characterization, using electron microscopy techniques and X-ray Absorption Fine Structure spectroscopy, was performed. HRTEM analysis showed the presence of Pd particles distributed in a narrow range with a mean diameter of about 2.5 nm while the XAFS analysis, confirmed the presence of the Pd nanoparticles but revealed also some alloying with Cu atoms.

  18. Green synthesis and characterization of Au@Pt core-shell bimetallic nanoparticles using gallic acid

    NASA Astrophysics Data System (ADS)

    Zhang, Guojun; Zheng, Hongmei; Shen, Ming; Wang, Lei; Wang, Xiaosan

    2015-06-01

    In this study, we developed a facile and benign green synthesis approach for the successful fabrication of well-dispersed urchin-like Au@Pt core-shell nanoparticles (NPs) using gallic acid (GA) as both a reducing and protecting agent. The proposed one-step synthesis exploits the differences in the reduction potentials of AuCl4- and PtCl62-, where the AuCl4- ions are preferentially reduced to Au cores and the PtCl62- ions are then deposited continuously onto the Au core surface as a Pt shell. The as-prepared Au@Pt NPs were characterized by transmission electron microscope (TEM); high-resolution transmission electron microscope (HR-TEM); scanning electron microscope (SEM); UV-vis absorption spectra (UV-vis); X-ray diffraction (XRD); Fourier transmission infrared spectra (FT-IR). We systematically investigated the effects of some experimental parameters on the formation of the Au@Pt NPs, i.e., the reaction temperature, the molar ratios of HAuCl4/H2PtCl6, and the amount of GA. When polyvinylpyrrolidone K-30 (PVP) was used as a protecting agent, the Au@Pt core-shell NPs obtained using this green synthesis method were better dispersed and smaller in size. The as-prepared Au@Pt NPs exhibited better catalytic activity in the reaction where NaBH4 reduced p-nitrophenol to p-aminophenol. However, the results showed that the Au@Pt bimetallic NPs had a lower catalytic activity than the pure Au NPs obtained by the same method, which confirmed the formation of Au@Pt core-shell nanostructures because the active sites on the surfaces of the Au NPs were covered with a Pt shell.

  19. Sustainable Strategy Utilizing Biomass: Visible-Light-Mediated Synthesis of γ-Valerolactone

    EPA Science Inventory

    A novel sustainable approach to valued γ-valerolactone is described that exploits visible light mediated conversion of biomass-derived levulinic acid using a bimetallic catalyst on graphitic carbon nitride, AgPd@g-C3N4.

  20. Structural models and atomic distribution of bimetallic nanoparticles as investigated by X-ray absorption spectroscopy.

    PubMed

    Hwang, Bing-Joe; Sarma, Loka Subramanyam; Chen, Jiun-Ming; Chen, Ching-Hsiang; Shih, Shou-Chu; Wang, Guo-Rung; Liu, Din-Goa; Lee, Jyh-Fu; Tang, Mau-Tsu

    2005-08-10

    In this report, we describe a general methodology to determine the extent of alloying or atomic distribution quantitatively in bimetallic nanoparticles (NPs) by X-ray absorption spectroscopy (XAS). The structural parameters determined in these studies serve as a quantitative index and provide a general route to determine the structural aspects of the bimetallic NPs. We have derived various types of possible structural models based on the extent of alloying and coordination number parameters of bimetallic NPs. We also discussed the nature of homo- and heterometallic interactions in bimetallic NPs based on the extent of alloying. Herein, we use carbon-supported platinum-ruthenium bimetallic nanoparticles to demonstrate the proposed methodology, and this can be extended further to get more insights into the alloying extent or atomic distribution of other bimetallic systems. The results demonstrated in this paper open up methods to determine the atomic distribution of bimetallic NPs, which is an extremely important parameter that strongly influences the physicochemical properties of NPs and their applications.

  1. XAFS characterization of Pt-Mo bimetallic catalysts for CO hydrogeneration

    SciTech Connect

    Choi, Sun Hee; Lee, Jae Sung

    1997-04-15

    Molybdenum-platinum bimetallic catalysts supported on alumina exhibited high activities in CO hydrogenation than supported monometallic catalysts of Mo or Pt. The structure of Mo-Pt bimetallic catalysts, which were prepared by incipient wetness impregnation of {gamma}-alumina with the variation of the order of Mo and Pt addition, was studied by XAFS and CO chemisorption. Since molybdenum contains overlapping contribution of the first and the second shells, EXAFS of these two shells and the first shell of platinum was analyzed for the bimetallic catalysts. EXAFS showed equivocally the formation of bimetallic bonds between Mo and Pt for all bimetallic catalysts. For all bimetallic catalysts, molybdenum seemed to segregate to the surface irrespective of the sequence of the impregnation. Strong interaction of Mo atoms with the support was also identified with EXAFS and XANES for both monometallic Mo catalysts and bimetallic catalysts. Regarding the activities of CO hydrogenation, it was concluded that reduced Mo sites were responsible for the high activity and that Pt helped Mo sites become more reduced. 28 refs., 6 figs., 5 tabs.

  2. Synthesis of Pt–Pd Core–Shell Nanostructures by Atomic Layer Deposition: Application in Propane Oxidative Dehydrogenation to Propylene

    SciTech Connect

    Lei, Yu; Liu, Bin; Lu, Junling; Lobo-Lapidus, Rodrigo J.; Wu, Tianpin; Feng, Hao; Xia, Xiaoxing; Mane, Anil U.; Libera, Joseph A.; Greeley, Jeffrey P.; Miller, Jeffrey T.; Elam, Jeffrey W.

    2012-08-20

    Atomic layer deposition (ALD) was employed to synthesize supported Pt–Pd bimetallic particles in the 1 to 2 nm range. The metal loading and composition of the supported Pt–Pd nanoparticles were controlled by varying the deposition temperature and by applying ALD metal oxide coatings to modify the support surface chemistry. High-resolution scanning transmission electron microscopy images showed monodispersed Pt–Pd nanoparticles on ALD Al2O3- and TiO2-modified SiO2 gel. X-ray absorption spectroscopy revealed that the bimetallic nanoparticles have a stable Pt-core, Pd-shell nanostructure. Density functional theory calculations revealed that the most stable surface configuration for the Pt–Pd alloys in an H2 environment has a Pt-core, Pd-shell nanostructure. Finally, in comparison to their monometallic counterparts, the small Pt–Pd bimetallic core–shell nanoparticles exhibited higher activity in propane oxidative dehydrogenation as compared to their physical mixture.

  3. TOPICAL REVIEW: Nanostructured catalysts in fuel cells

    NASA Astrophysics Data System (ADS)

    Zhong, Chuan-Jian; Luo, Jin; Fang, Bin; Wanjala, Bridgid N.; Njoki, Peter N.; Loukrakpam, Rameshwori; Yin, Jun

    2010-02-01

    One of the most important challenges for the ultimate commercialization of fuel cells is the preparation of active, robust, and low-cost catalysts. This review highlights some findings of our investigations in the last few years in developing advanced approaches to nanostructured catalysts that address this challenge. Emphasis is placed on nanoengineering-based fabrication, processing, and characterization of multimetallic nanoparticles with controllable size (1-10 nm), shape, composition (e.g. MlnM2100-n, M1nM2mM3100-n-m, M1@M2, where M (1 or 2) = Pt, Co, Ni, V, Fe, Cu, Pd, W, Ag, Au etc) and morphology (e.g. alloy, core@shell etc). In addition to an overview of the fundamental issues and the recent progress in fuel cell catalysts, results from evaluations of the electrocatalytic performance of nanoengineered catalysts in fuel cell reactions are discussed. This approach differs from other traditional approaches to the preparation of supported catalysts in the ability to control the particle size, composition, phase, and surface properties. An understanding of how the nanoscale properties of the multimetallic nanoparticles differ from their bulk-scale counterparts, and how the interaction between the nanoparticles and the support materials relates to the size sintering or evolution in the thermal activation process, is also discussed. The fact that the bimetallic gold-platinum nanoparticle system displays a single-phase character different from the miscibility gap known for its bulk-scale counterpart serves as an important indication of the nanoscale manipulation of the structural properties, which is useful for refining the design and preparation of the bimetallic catalysts. The insight gained from probing how nanoparticle-nanoparticle and nanoparticle-substrate interactions relate to the size evolution in the activation process of nanoparticles on planar substrates serves as an important guiding principle in the control of nanoparticle sintering on different

  4. Physical and Numerical Analysis of Extrusion Process for Production of Bimetallic Tubes

    SciTech Connect

    Misiolek, W.Z.; Sikka, V.K.

    2006-08-10

    Bimetallic tubes are used for very specific applications where one of the two metals provides strength and the other provides specific properties such as aqueous corrosion and carburization, coking resistance, and special electrical and thermal properties. Bimetallic tubes have application in pulp and paper industry for heat-recovery boilers, in the chemical industry for ethylene production, and in the petrochemical industry for deep oil well explorations. Although bimetallic tubes have major applications in energy-intensive industry, they often are not used because of their cost and manufacturing sources in the United States. This project was intended to address both of these issues.

  5. Twisted Graphene Nanostructures

    NASA Astrophysics Data System (ADS)

    Gani, Satrio; Virgus, Yudistira; Rossi, Enrico

    2015-03-01

    Recent advances in fabrication techniques have made possible the realization of graphene nanostructures with atomic precision. Some of the nanostructures realized are completely novel. We study the electronic properties of such novel graphene nanostructures when deposited on two dimensional crystals. In particular we study the case when the two dimensional crystal is graphene, or bilayer graphene. We obtain results for the nanostructure electronic spectrum and find how the spectrum is affected by the coupling between the nanostructure and the two-dimensional substrate. In particular we study how the ``twist'' angle between the graphene nanostructure and the two-dimensional crystal affects the spectrum of the nanostructure. Work supported by ONR-N00014-13-1-0321 and ACS-PRF # 53581-DNI5.

  6. Dechlorination of Polychlorinated Biphenyls by Pd/Mg Bimetallic Corrosion Nano-Cells

    EPA Science Inventory

    Polychlorinated biphenyls (PCBs), manufactured until mid-1970's for use as electrical insulators, were banned in 1979 due to their toxicity and persistence in the environment (1). Dechlorination of PCBs using bimetallic systems is a promising technology wherein enhanced corrosio...

  7. Facile synthesis of Cu-Pd bimetallic multipods for application in cyclohexane oxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuo-Qun; Huang, Jianliu; Zhang, Lan; Sun, Mei; Wang, You-Cheng; Lin, Yue; Zeng, Jie

    2014-10-01

    The synergy between Cu and Pd makes Cu-Pd bimetallic nanocrystals interesting materials for investigation. The scarcity of shapes of Cu-Pd bimetallic nanocrystals motivated us to explore highly branched structures, which may promote a wide range of applications. In this communication, we report a facile synthesis of Cu-Pd bimetallic multipods (19.2 ± 1.2 nm), on branches of which some high-index facets were exposed. Modification of reaction parameters concerning capping agents and reductant led to the formation of other shapes, including sphere-like nanocrystals (SNCs). When loaded onto TiO2, the as-prepared Cu-Pd bimetallic multipods exhibited excellent catalytic activity for the oxidation of cyclohexane by hydrogen peroxide and higher selectivity towards cyclohexanone than monometallic catalysts and SNCs/TiO2.

  8. Levelling the playing field: screening for synergistic effects in coalesced bimetallic nanoparticles.

    PubMed

    Tan, Rachel Lee Siew; Song, Xiaohui; Chen, Bo; Chong, Wen Han; Fang, Yin; Zhang, Hua; Wei, Jun; Chen, Hongyu

    2016-02-14

    Depending on the synthetic methods, bimetallic nanoparticles can have either core-shell, phase segregated, alloy, or partially coalesced structures, presenting different degrees of atomic mixing on their surface. Along with the variations of size and morphology, the structural differences make it difficult to compare the catalytic activity of bimetallic nanoparticles. In this article, we developed a facile screening method that can focus on the synergistic effects rather than structural differences. Prefabricated nanoparticles are mixed together to form linear aggregates and coalesced to form bimetallic junctions. Their hollow silica shells allow materials transport but prevent further aggregation. With a level playing field, this screening platform can identify the best bimetallic combination for a catalytic reaction, before optimizing the synthesis. This approach is more advantageous than the conventional approaches where structural difference may have dominant effects on the catalytic performance. PMID:26797095

  9. Facile synthesis of Cu-Pd bimetallic multipods for application in cyclohexane oxidation.

    PubMed

    Zhang, Zhuo-Qun; Huang, Jianliu; Zhang, Lan; Sun, Mei; Wang, You-Cheng; Lin, Yue; Zeng, Jie

    2014-10-31

    The synergy between Cu and Pd makes Cu-Pd bimetallic nanocrystals interesting materials for investigation. The scarcity of shapes of Cu-Pd bimetallic nanocrystals motivated us to explore highly branched structures, which may promote a wide range of applications. In this communication, we report a facile synthesis of Cu-Pd bimetallic multipods (19.2 ± 1.2 nm), on branches of which some high-index facets were exposed. Modification of reaction parameters concerning capping agents and reductant led to the formation of other shapes, including sphere-like nanocrystals (SNCs). When loaded onto TiO2, the as-prepared Cu-Pd bimetallic multipods exhibited excellent catalytic activity for the oxidation of cyclohexane by hydrogen peroxide and higher selectivity towards cyclohexanone than monometallic catalysts and SNCs/TiO2. PMID:25297725

  10. Chemistry of Bimetallic Linked Cyclopentadienyl Complexes: Progress Report, 1 December 1986 --30 November 1989

    DOE R&D Accomplishments Database

    Schrock, R. R.

    1989-01-01

    Research continued on the chemistry and preparation of bimetallic cyclopentadienyl complexes containing up to two tungsten or one tungsten and a cobalt, rhodium, or ruthenium. The general method for preparation and analysis of polyenes is also discussed. (CBS)

  11. Levelling the playing field: screening for synergistic effects in coalesced bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Tan, Rachel Lee Siew; Song, Xiaohui; Chen, Bo; Chong, Wen Han; Fang, Yin; Zhang, Hua; Wei, Jun; Chen, Hongyu

    2016-02-01

    Depending on the synthetic methods, bimetallic nanoparticles can have either core-shell, phase segregated, alloy, or partially coalesced structures, presenting different degrees of atomic mixing on their surface. Along with the variations of size and morphology, the structural differences make it difficult to compare the catalytic activity of bimetallic nanoparticles. In this article, we developed a facile screening method that can focus on the synergistic effects rather than structural differences. Prefabricated nanoparticles are mixed together to form linear aggregates and coalesced to form bimetallic junctions. Their hollow silica shells allow materials transport but prevent further aggregation. With a level playing field, this screening platform can identify the best bimetallic combination for a catalytic reaction, before optimizing the synthesis. This approach is more advantageous than the conventional approaches where structural difference may have dominant effects on the catalytic performance.Depending on the synthetic methods, bimetallic nanoparticles can have either core-shell, phase segregated, alloy, or partially coalesced structures, presenting different degrees of atomic mixing on their surface. Along with the variations of size and morphology, the structural differences make it difficult to compare the catalytic activity of bimetallic nanoparticles. In this article, we developed a facile screening method that can focus on the synergistic effects rather than structural differences. Prefabricated nanoparticles are mixed together to form linear aggregates and coalesced to form bimetallic junctions. Their hollow silica shells allow materials transport but prevent further aggregation. With a level playing field, this screening platform can identify the best bimetallic combination for a catalytic reaction, before optimizing the synthesis. This approach is more advantageous than the conventional approaches where structural difference may have dominant

  12. Diverse melting modes and structural collapse of hollow bimetallic core-shell nanoparticles: a perspective from molecular dynamics simulations.

    PubMed

    Huang, Rao; Shao, Gui-Fang; Zeng, Xiang-Ming; Wen, Yu-Hua

    2014-11-14

    Introducing hollow structures into metallic nanoparticles has become a promising route to improve their catalytic performances. A fundamental understanding of thermal stability of these novel nanostructures is of significance for their syntheses and applications. In this article, molecular dynamics simulations have been employed to offer insights into the thermodynamic evolution of hollow bimetallic core-shell nanoparticles. Our investigation reveals that for hollow Pt-core/Au-shell nanoparticle, premelting originates at the exterior surface, and a typical two-stage melting behavior is exhibited, similar to the solid ones. However, since the interior surface provides facilitation for the premelting initiating at the core, the two-stage melting is also observed in hollow Au-core/Pt-shell nanoparticle, remarkably different from the solid one. Furthermore, the collapse of hollow structure is accompanied with the overall melting of the hollow Pt-core/Au-shell nanoparticle while it occurs prior to that of the hollow Au-core/Pt-shell nanoparticle and leads to the formation of a liquid-core/solid-shell structure, although both of them finally transform into a mixing alloy with Au-dominated surface. Additionally, the existence of stacking faults in the hollow Pt-core/Au-shell nanoparticle distinctly lowers its melting point. This study could be of great importance to the design and development of novel nanocatalysts with both high activity and excellent stability.

  13. Diverse Melting Modes and Structural Collapse of Hollow Bimetallic Core-Shell Nanoparticles: A Perspective from Molecular Dynamics Simulations

    PubMed Central

    Huang, Rao; Shao, Gui-Fang; Zeng, Xiang-Ming; Wen, Yu-Hua

    2014-01-01

    Introducing hollow structures into metallic nanoparticles has become a promising route to improve their catalytic performances. A fundamental understanding of thermal stability of these novel nanostructures is of significance for their syntheses and applications. In this article, molecular dynamics simulations have been employed to offer insights into the thermodynamic evolution of hollow bimetallic core-shell nanoparticles. Our investigation reveals that for hollow Pt-core/Au-shell nanoparticle, premelting originates at the exterior surface, and a typical two-stage melting behavior is exhibited, similar to the solid ones. However, since the interior surface provides facilitation for the premelting initiating at the core, the two-stage melting is also observed in hollow Au-core/Pt-shell nanoparticle, remarkably different from the solid one. Furthermore, the collapse of hollow structure is accompanied with the overall melting of the hollow Pt-core/Au-shell nanoparticle while it occurs prior to that of the hollow Au-core/Pt-shell nanoparticle and leads to the formation of a liquid-core/solid-shell structure, although both of them finally transform into a mixing alloy with Au-dominated surface. Additionally, the existence of stacking faults in the hollow Pt-core/Au-shell nanoparticle distinctly lowers its melting point. This study could be of great importance to the design and development of novel nanocatalysts with both high activity and excellent stability. PMID:25394424

  14. Lattice-matched bimetallic CuPd-graphene nanocatalysts for facile conversion of biomass-derived polyols to chemicals.

    PubMed

    Jin, Xin; Dang, Lianna; Lohrman, Jessica; Subramaniam, Bala; Ren, Shenqiang; Chaudhari, Raghunath V

    2013-02-26

    A bimetallic nanocatalyst with unique surface configuration displays extraordinary performance for converting biomass-derived polyols to chemicals, with potentially much broader applications in the design of novel catalysts for several reactions of industrial relevance. The synthesis of nanostructured metal catalysts containing a large population of active surface facets is critical to achieve high activity and selectivity in catalytic reactions. Here, we describe a new strategy for synthesizing copper-based nanocatalysts on reduced graphene oxide support in which the catalytically active {111} facet is achieved as the dominant surface by lattice-match engineering. This method yields highly active Cu-graphene catalysts (turnover frequency = 33-114 mol/g atom Cu/h) for converting biopolyols (glycerol, xylitol, and sorbitol) to value-added chemicals, such as lactic acid and other useful co-products consisting of diols and linear alcohols. Palladium incorporation in the Cu-graphene system in trace amounts results in a tandem synergistic system in which the hydrogen generated in situ from polyols is used for sequential hydrogenolysis of the feedstock itself. Furthermore, the Pd addition remarkably enhances the overall stability of the nanocatalysts. The insights gained from this synthetic methodology open new vistas for exploiting graphene-based supports to develop novel and improved metal-based catalysts for a variety of heterogeneous catalytic reactions. PMID:23297693

  15. Segregation and shape stability in small bimetallic particles

    NASA Astrophysics Data System (ADS)

    Morán-López, J. L.; Balseiro, C. A.

    1986-04-01

    The equilibrium atomic spatial distribution of a 55-atom bimetallic particle is studied within the regular solution model. As a consequence of the large surface-to-volume ratio, the criterion for phase separation versus long-range ordering in small particles and in infinite systems differs considerably. With the comparison of the total energies in cubo-octahedral (C) and icosahedral (I) particles, a phase diagram for the ground state is obtained. As a function of temperature the particle may change its shape from C to I. We applied the theory, based on estimations from bulk properties, to the CuPd and the IrPd particles, and present results for the temperature dependence of the average concentrations at the different shells around the central atom. On the same basis some predictions for the NiPt, CuPt, AuPt, and the CuNi systems are made.

  16. Patched bimetallic surfaces are active catalysts for ammonia decomposition

    PubMed Central

    Guo, Wei; Vlachos, Dionisios G.

    2015-01-01

    Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core–shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core–shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N−H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design. PMID:26443525

  17. Ostwald-Driven Phase Separation in Bimetallic Nanoparticle Assemblies.

    PubMed

    Prévot, Geoffroy; Nguyen, Nhat Tai; Alloyeau, Damien; Ricolleau, Christian; Nelayah, Jaysen

    2016-04-26

    The compositional stability of bimetallic nanoparticles (NPs) is crucial for many applications. We have studied the coarsening of amorphous carbon-supported Au-Pd NPs during annealing at 873 K. Using scanning transmission electron microscopy and energy-dispersive spectroscopy measurements, we show that, despite a complete miscibility of the two metals, the particle assembly undergoes a phase separation during annealing, which leads to two distinct populations: Au-rich NPs with a mean radius of 3.5 nm and large Pd-rich NPs with a mean radius of 25 nm. Thermodynamic calculations and kinetic Monte Carlo simulations explain this behavior that is driven by the competition between surface and mixing energy and by the different mobilities of the two atomic species. PMID:26989906

  18. Patched bimetallic surfaces are active catalysts for ammonia decomposition

    SciTech Connect

    Guo, Wei; Vlachos, Dionisios G.

    2015-10-07

    In this study, ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material’s structure. Core–shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core–shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

  19. Synthesis and characterization of carboxyethylene-bridged bimetallic compounds

    SciTech Connect

    Gibson, D.H.; Franco, J.O.; Mehta, J.M.; Harris, M.T.; Ding, Y.; Mashuta, M.S.; Richardson, J.F.

    1995-11-01

    The synthesis and characterization of carboxyethylene-bridged bimetallic complexes Cp{sup *}Re(CO)(NO)CO{sub 2}CH{sub 2}CH{sub 2}M (4, M = Mo(CO){sub 3}Cp; 7, M = W(CO){sub 3}Cp; 9, M = Fe(CO){sub 2}Cp) and CpFe(CO)(PPh{sub 3})CO{sub 2}CH{sub 2}CH{sub 2}W(CO){sub 3}Cp (11) are described. Thermolysis of 4, in solution or in the solid state, yields the CO{sub 2}-bridged compound Cp{sup *}Re(CO)(NO)(CO{sub 2} )Mo(CO){sub 2}Cp (3) as the major product. Compound 11 has been structurally characterized. Crystal data for 11 are reported. 16 refs., 1 fig., 3 tabs.

  20. Patched bimetallic surfaces are active catalysts for ammonia decomposition.

    PubMed

    Guo, Wei; Vlachos, Dionisios G

    2015-10-07

    Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core-shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core-shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

  1. The selective hydrogenation of crotonaldehyde over bimetallic catalysts

    SciTech Connect

    Schoeb, A.M.

    1997-02-01

    The selective hydrogenation of crotonaldehyde has been investigated over a monometallic Pt/SiO{sub 2} catalyst and platinum bimetallic catalysts where the second metal was either silver, copper, or tin. The effects of addition of a second metal to the Pt/SiO{sub 2} system on the selectivity to crotyl alcohol were investigated. The Pt-Sn bimetallic catalysts were characterized by hydrogen chemisorption, {sup 1}H NMR and microcalorimetry. The Pt-Ag/SiO{sub 2} and Pt-Cu/SiO{sub 2} catalysts were characterized by hydrogen chemisorption. Pt-Sn/SiO{sub 2} catalysts selectively hydrogenated crotonaldehyde to crotyl alcohol and the method of preparation of these catalysts affected the selectivity. The most selective Pt-Sn/SiO{sub 2} catalysts for the hydrogenation of crotonaldehyde to crotyl alcohol were those in which the Sn precursor was dissolved in a HCl solution. Sn increased both the rate of formation of butyraldehyde and the rate of formation of crotyl alcohol. The Pt/SiO{sub 2}, Pt-Ag/SiO{sub 2} and Pt-Cu/SiO{sub 2} catalysts produced only butyraldehyde. Initial heats of adsorption ({approximately}90 kJ/mol) measured using microcalorimetry were not affected by the presence of Sn on Pt. We can conclude that there is no through metal electronic interaction between Pt and Sn at least with respect to hydrogen surface bonds since the Pt and Pt-Sn at least with respect to hydrogen surface bonds since the Pt and Pt-Sn had similar initial heats of adsorption coupled with the invariance of the {sup 1}H NMR Knight shift.

  2. (Gold core)@(ceria shell) nanostructures for plasmon-enhanced catalytic reactions under visible light.

    PubMed

    Li, Benxia; Gu, Ting; Ming, Tian; Wang, Junxin; Wang, Peng; Wang, Jianfang; Yu, Jimmy C

    2014-08-26

    Driving catalytic reactions with sunlight is an excellent example of sustainable chemistry. A prerequisite of solar-driven catalytic reactions is the development of photocatalysts with high solar-harvesting efficiencies and catalytic activities. Herein, we describe a general approach for uniformly coating ceria on monometallic and bimetallic nanocrystals through heterogeneous nucleation and growth. The method allows for control of the shape, size, and type of the metal core as well as the thickness of the ceria shell. The plasmon shifts of the Au@CeO2 nanostructures resulting from the switching between Ce(IV) and Ce(III) are observed. The selective oxidation of benzyl alcohol to benzaldehyde, one of the fundamental reactions for organic synthesis, performed under both broad-band and monochromatic light, demonstrates the visible-light-driven catalytic activity and reveals the synergistic effect on the enhanced catalysis of the Au@CeO2 nanostructures.

  3. Nanostructured composite reinforced material

    DOEpatents

    Seals, Roland D.; Ripley, Edward B.; Ludtka, Gerard M.

    2012-07-31

    A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

  4. Bimetallic 3D nanostar dimers in ring cavities: recyclable and robust surface-enhanced Raman scattering substrates for signal detection from few molecules.

    PubMed

    Gopalakrishnan, Anisha; Chirumamilla, Manohar; De Angelis, Francesco; Toma, Andrea; Zaccaria, Remo Proietti; Krahne, Roman

    2014-08-26

    Top-down fabrication of electron-beam lithography (EBL)-defined metallic nanostructures is a successful route to obtain extremely high electromagnetic field enhancement via plasmonic effects in well-defined regions. To this aim, various geometries have been introduced such as disks, triangles, dimers, rings, self-similar lenses, and more. In particular, metallic dimers are highly efficient for surface-enhanced Raman spectroscopy (SERS), and their decoupling from the substrate in a three-dimensional design has proven to further improve their performance. However, the large fabrication time and cost has hindered EBL-defined structures from playing a role in practical applications. Here we present three-dimensional nanostar dimer devices that can be recycled via maskless metal etching and deposition processes, due to conservation of the nanostructure pattern in the 3D geometry of the underlying Si substrate. Furthermore, our 3D-nanostar-dimer-in-ring structures (3D-NSDiRs) incorporate several advantageous aspects for SERS by enhancing the performance of plasmonic dimers via an external ring cavity, by efficient decoupling from the substrate through an elevated 3D design, and by bimetallic AuAg layers that exploit the increased performance of Ag while maintaining the biocompatibility of Au. We demonstrate SERS detection on rhodamine and adenine at extremely low density up to the limit of few molecules and analyze the field enhancement of the 3D-NSDiRs with respect to the exciting wavelength and metal composition.

  5. Bimetallic Au-decorated Pd catalyst for the liquid phase hydrodechlorination of 2,4-dichlorophenol

    NASA Astrophysics Data System (ADS)

    Zhou, Juan; Chen, Huan; Chen, Quanyuan; Huang, Zhaolu

    2016-11-01

    Monometallic and bimetallic Pd-Au catalysts supported on multi-walled carbon nanotubes (CNTs) with varied Au cooperation amounts were prepared using the complexing-reduction method in the presence of tetrahydrofuran (THF). The liquid phase catalytic hydrodechlorination (HDC) of 2,4-dichlorophenol (2,4-DCP) was investigated over these bimetallic catalysts. The catalysts were characterized by N2 adsorption-desorption isotherms, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and H2 chemisorption. Characterization results showed that the co-reduction of Pd and Au mainly formed alloy-like structure. The bimetallic catalysts had smaller metal particles and larger numbers of exposed active site than that of monometallic catalysts. In addition, compared with Pd(1.7)/CNTs and Au(0.4)/CNTs, the binding energies of Pd 3d5/2 shifted to higher positions while that of Au 4f7/2 had negative shifts in the Pd-Au bimetallic catalysts, which can be ascribed to the electrons transferred from metal Pd to Au and the cationization of Pd particles was enhanced. Accordingly, the bimetallic Pd-Au particles with different Au contents in the catalysts exhibited varied synergistic effects for the catalytic HDC of 2,4-DCP, with Pd(1.8)Au(0.4)/CNTs having the highest catalytic activity. For the bimetallic catalysts, a disproportional increase of turnover frequency (TOF) was observed with increasing Au content due to the enhanced cationization of Pd particles. Moreover, the dechlorination of 2,4-DCP over the supported monometallic and bimetallic catalysts proceeded via both the stepwise and concerted pathway, and the concerted pathway became predominant with Au decoration amount in the catalyst.

  6. Peptide-Directed PdAu Nanoscale Surface Segregation: Toward Controlled Bimetallic Architecture for Catalytic Materials.

    PubMed

    Bedford, Nicholas M; Showalter, Allison R; Woehl, Taylor J; Hughes, Zak E; Lee, Sungsik; Reinhart, Benjamin; Ertem, S Piril; Coughlin, E Bryan; Ren, Yang; Walsh, Tiffany R; Bunker, Bruce A

    2016-09-27

    Bimetallic nanoparticles are of immense scientific and technological interest given the synergistic properties observed when two different metallic species are mixed at the nanoscale. This is particularly prevalent in catalysis, where bimetallic nanoparticles often exhibit improved catalytic activity and durability over their monometallic counterparts. Yet despite intense research efforts, little is understood regarding how to optimize bimetallic surface composition and structure synthetically using rational design principles. Recently, it has been demonstrated that peptide-enabled routes for nanoparticle synthesis result in materials with sequence-dependent catalytic properties, providing an opportunity for rational design through sequence manipulation. In this study, bimetallic PdAu nanoparticles are synthesized with a small set of peptides containing known Pd and Au binding motifs. The resulting nanoparticles were extensively characterized using high-resolution scanning transmission electron microscopy, X-ray absorption spectroscopy, and high-energy X-ray diffraction coupled to atomic pair distribution function analysis. Structural information obtained from synchrotron radiation methods was then used to generate model nanoparticle configurations using reverse Monte Carlo simulations, which illustrate sequence dependence in both surface structure and surface composition. Replica exchange with solute tempering molecular dynamics simulations were also used to predict the modes of peptide binding on monometallic surfaces, indicating that different sequences bind to the metal interfaces via different mechanisms. As a testbed reaction, electrocatalytic methanol oxidation experiments were performed, wherein differences in catalytic activity are clearly observed in materials with identical bimetallic composition. Taken together, this study indicates that peptides could be used to arrive at bimetallic surfaces with enhanced catalytic properties, which could be leveraged

  7. Synthesis of branched metal nanostructures with controlled architecture and composition

    NASA Astrophysics Data System (ADS)

    Ortiz, Nancy

    On account of their small size, metal nanoparticles are proven to be outstanding catalysts for numerous chemical transformations and represent promising platforms for applications in the fields of electronics, chemical sensing, medicine, and beyond. Many properties of metal nanoparticles are size-dependent and can be further manipulated through their shape and architecture (e.g., spherical vs. branched). Achieving morphology control of nanoparticles through solution-based techniques has proven challenging due to limited knowledge of morphology development in nanosyntheses. To overcome these complications, a systematic examination of the local ligand environment of metal precursors on nanostructure formation was undertaken to evaluate its contribution to nanoparticle nucleation rate and subsequent growth processes. Specifically, this thesis will provide evidence from ex situ studies---Transmission Electron Microscopy (TEM) and UV-visible spectroscopy (UV-Vis)---that support the hypothesis that strongly coordinated ligands delay burst-like nucleation to generate spherical metal nanoparticles and ligands with intermediate binding affinity regulate the gradual reduction of metal precursors to promote aggregated assembly of nanodendrites. These ex situ studies were coupled with a new in situ perspective, providing detailed understanding of metal precursor transformation, its direct relation to nanoparticle morphology development, and the ligand influence towards the formation of structurally complex metal nanostructures, using in situ synchrotron X-ray Diffraction (XRD) and Ultra Small-Angle X-ray Scattering (USAXS). The principles extracted from the study of monometallic nanostructure formation were also found to be generally applicable to the synthesis of bimetallic nanostructures, e.g., Pd-Pt architectures, with either core-shell or alloyed structures that were readily achieved by ligand selection. These outcomes provide a direct connection between fundamental

  8. Impact of Multifunctional Bimetallic Materials on Lithium Battery Electrochemistry.

    PubMed

    Durham, Jessica L; Poyraz, Altug S; Takeuchi, Esther S; Marschilok, Amy C; Takeuchi, Kenneth J

    2016-09-20

    Electric energy storage devices such as batteries are complex systems comprised of a variety of materials with each playing separate yet interactive roles, complicated by length scale interactions occurring from the molecular to the mesoscale. Thus, addressing specific battery issues such as functional capacity requires a comprehensive perspective initiating with atomic level concepts. For example, the electroactive materials which contribute to the functional capacity in a battery comprise approximately 30% or less of the total device mass. Thus, the design and implementation of multifunctional materials can conceptually reduce or eliminate the contribution of passive materials to the size and mass of the final system. Material multifunctionality can be achieved through appropriate material design on the atomic level resulting in bimetallic electroactive materials where one metal cation forms mesoscale conductive networks upon discharge while the other metal cations can contribute to atomic level structure and net functional secondary capacity, a device level issue. Specifically, this Account provides insight into the multimechanism electrochemical redox processes of bimetallic cathode materials based on transition metal oxides (MM'O) or phosphorus oxides (MM'PO) where M = Ag and M' = V or Fe. One discharge process can be described as reduction-displacement where Ag(+) is reduced to Ag(0) and displaced from the parent structure. This reduction-displacement reaction in silver-containing bimetallic electrodes allows for the in situ formation of a conductive network, enhancing the electrochemical performance of the electrode and reducing or eliminating the need for conductive additives. A second discharge process occurs through the reduction of the second transition metal, V or Fe, where the oxidation state of the metal center is reduced and lithium cations are inserted into the structure. As both metal centers contribute to the functional capacity, determining the

  9. Impact of Multifunctional Bimetallic Materials on Lithium Battery Electrochemistry.

    PubMed

    Durham, Jessica L; Poyraz, Altug S; Takeuchi, Esther S; Marschilok, Amy C; Takeuchi, Kenneth J

    2016-09-20

    Electric energy storage devices such as batteries are complex systems comprised of a variety of materials with each playing separate yet interactive roles, complicated by length scale interactions occurring from the molecular to the mesoscale. Thus, addressing specific battery issues such as functional capacity requires a comprehensive perspective initiating with atomic level concepts. For example, the electroactive materials which contribute to the functional capacity in a battery comprise approximately 30% or less of the total device mass. Thus, the design and implementation of multifunctional materials can conceptually reduce or eliminate the contribution of passive materials to the size and mass of the final system. Material multifunctionality can be achieved through appropriate material design on the atomic level resulting in bimetallic electroactive materials where one metal cation forms mesoscale conductive networks upon discharge while the other metal cations can contribute to atomic level structure and net functional secondary capacity, a device level issue. Specifically, this Account provides insight into the multimechanism electrochemical redox processes of bimetallic cathode materials based on transition metal oxides (MM'O) or phosphorus oxides (MM'PO) where M = Ag and M' = V or Fe. One discharge process can be described as reduction-displacement where Ag(+) is reduced to Ag(0) and displaced from the parent structure. This reduction-displacement reaction in silver-containing bimetallic electrodes allows for the in situ formation of a conductive network, enhancing the electrochemical performance of the electrode and reducing or eliminating the need for conductive additives. A second discharge process occurs through the reduction of the second transition metal, V or Fe, where the oxidation state of the metal center is reduced and lithium cations are inserted into the structure. As both metal centers contribute to the functional capacity, determining the

  10. A novel and greener approach for shape controlled synthesis of gold and gold-silver core shell nanostructure and their application in optical coatings

    NASA Astrophysics Data System (ADS)

    Sinha, Tanur; Ahmaruzzaman, M.

    2015-06-01

    Green and facile synthetic methods have gained marvellous fame for the production of polyhedral, anisotropic and spherical gold, and gold-silver bimetallic nanostructures. The useful pivotal characteristics of a green procedure are the usage of environment benign solvent medium, reducing and stabilising agents, and shorter reaction time. We describe here a novel, and greener method for the production of gold and gold-silver core shell nanostructures using aqueous fish scales extract of the Labeo rohita. The effect of various reaction parameters, such as temperature and concentration for the synthesis of the nanostructures were studied. Results indicated that triangular and decahedron gold nanostructures were formed at a lower temperature (40 °C) and concentration (10%). While, icosahedral and spherical gold nanostructures were produced at a comparatively higher temperature (100 °C) and concentration (40%). The study also revealed that the core-shell bimetallic nanostructures with different morphologies (spherical and oval-shape) were formed at different ratios of chloroaurate and silver nitrate solution. Thus, the present study indicated a simple shape controlled synthesis of gold and gold silver core-shell nanostructures. The synthesised gold nanotriangles were coated over the glass substrate and found to be highly efficient in absorbing infra-red radiations for potential architectural applications. Therefore, the study demonstrated the facile usage of gold nanotriangles for optical coatings. The present strategy depicted the dual functional ability of the fish scale extract as reducing and stabilising agents. This strategy also eliminates the usage of hazardous chemicals, toxic solvents and harsh reducing and stabilizing agents.

  11. A novel and greener approach for shape controlled synthesis of gold and gold-silver core shell nanostructure and their application in optical coatings.

    PubMed

    Sinha, Tanur; Ahmaruzzaman, M

    2015-06-15

    Green and facile synthetic methods have gained marvellous fame for the production of polyhedral, anisotropic and spherical gold, and gold-silver bimetallic nanostructures. The useful pivotal characteristics of a green procedure are the usage of environment benign solvent medium, reducing and stabilising agents, and shorter reaction time. We describe here a novel, and greener method for the production of gold and gold-silver core shell nanostructures using aqueous fish scales extract of the Labeo rohita. The effect of various reaction parameters, such as temperature and concentration for the synthesis of the nanostructures were studied. Results indicated that triangular and decahedron gold nanostructures were formed at a lower temperature (40°C) and concentration (10%). While, icosahedral and spherical gold nanostructures were produced at a comparatively higher temperature (100°C) and concentration (40%). The study also revealed that the core-shell bimetallic nanostructures with different morphologies (spherical and oval-shape) were formed at different ratios of chloroaurate and silver nitrate solution. Thus, the present study indicated a simple shape controlled synthesis of gold and gold silver core-shell nanostructures. The synthesised gold nanotriangles were coated over the glass substrate and found to be highly efficient in absorbing infra-red radiations for potential architectural applications. Therefore, the study demonstrated the facile usage of gold nanotriangles for optical coatings. The present strategy depicted the dual functional ability of the fish scale extract as reducing and stabilising agents. This strategy also eliminates the usage of hazardous chemicals, toxic solvents and harsh reducing and stabilizing agents.

  12. Size-depressed critical temperatures for the order-disorder transition of FePt, CoPt, FePb, Cu2S, and ZnS nanostructures

    NASA Astrophysics Data System (ADS)

    Jiang, R.; Zhou, Z. F.; Yang, X. X.; Guo, N. G.; Qi, W. H.; Sun, C. Q.

    2013-01-01

    The size dependency of the critical temperature (TC) for the order-disorder phase transitions of both the bimetallic and the chalcogenide nanoclusters is shown to follow the rule of bond order-length-strength correlation. The loss of the cohesive energy of the undercoordinated atoms in the surface skin dictates the structural stability. Theoretical reproduction of the size TC trends of FePt, CoPt, FePb, Cu2S, and ZnS nanostructures not only confirms our expectations without involving the concepts of surface energy or entropy used for continuum bulk materials but also provides guideline for engineering nanostructured alloys or compounds.

  13. Fracture evaluations of fusion line cracks in nuclear pipe bimetallic welds

    SciTech Connect

    Scott, P.; Francini, R.; Rahman, S.; Rosenfield, A.; Wilkowski, G.

    1995-04-01

    In both BWRs and PWRs there are many locations where carbon steel pipe or components are joined to stainless steel pipe or components with a bimetallic weld. The objective of the research described in this report was to assess the accuracy of current fracture analyses for the case of a crack along a carbon steel to austenitic weld fusion line. To achieve the program objective, material property data and data from a large-diameter pipe fracture experiment were developed to assess current analytical methods. The bimetallic welds evaluated in this program were bimetallic welds obtained from a cancelled Combustion Engineering plant. The welds joined sections of the carbon steel cold-leg piping system to stainless steel safe ends that were to be welded to stainless steel pump housings. The major conclusion drawn as a result of these efforts was that the fracture behavior of the bimetallic weld evaluated in this program could be evaluated with reasonable accuracy using the strength and toughness properties of the carbon steel pipe material in conjunction with conventional elastic-plastic fracture mechanics or limit-load analyses. This may not be generally true for all bimetallic welds, as discussed in this report.

  14. Characterization of Bimetallic Fe-Ru Oxide Nanoparticles Prepared by Liquid-Phase Plasma Method

    NASA Astrophysics Data System (ADS)

    Lee, Sung-Jin; Lee, Heon; Jeon, Ki-Joon; Park, Hyunwoong; Park, Young-Kwon; Jung, Sang-Chul

    2016-07-01

    The bimetallic Fe-Ru oxide nanoparticles were synthesized in the liquid-phase plasma (LPP) method which employed iron chloride and ruthenium chloride as precursors. The active species (OH·, Hα, Hβ, and OI) and the iron and ruthenium ions were observed in the plasma field created by the LPP process. The spherical-shaped bimetallic Fe-Ru oxide nanoparticles were synthesized by the LPP reaction, and the size of the particles was growing along with the progression of the LPP reaction. The synthesized bimetallic Fe-Ru oxide nanoparticles were comprised of Fe2O3, Fe3O4, RuO, and RuO2. Ruthenium had a higher reduction potential than iron and resulted in higher ruthenium composition in the synthesized bimetallic nanoparticles. The control of the molar ratio of the precursors in the reactant solution was found to be employed as a means to control the composition of the elements in bimetallic nanoparticles.

  15. Effect of Synthesis Techniques on Crystallization and Optical Properties of Ag-Cu Bimetallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Xiong, Ziye; Qin, Fen; Huang, Po-Shun; Nettleship, Ian; Lee, Jung-Kun

    2016-04-01

    Silver (Ag)-copper (Cu) bimetallic nanoparticles (NPs) were synthesized by the reduction of silver nitrate and copper (II) acetate monohydrate using ethylene glycol in a microwave (MW) heating system with controlled reaction times ranging from 5 min to 30 min. The molar ratio Ag/Cu was varied from 1:1 to 1:3. The effect of reaction conditions on the bimetallic NPs structures and compositions were characterized by x-ray photoelectron spectroscopy, x-ray diffraction and transmission electron microscopy. The average particle size was approximately 150 nm. The surface plasmon resonance (SPR) of Ag-Cu bimetallic NPs was investigated by monitoring the SPR band peak behavior via UV/Vis spectrophotometry. The resonance peak positions and peak widths varied due to the different structures of the bimetallic NPs created under the synthesis conditions. In the MW heating method, the reduction of Cu was increased and Cu was inhomogeneously deposited over the Ag cores. As the composition of Cu becoming higher in the Ag-Cu bimetallic NPs, the absorption between 400 nm to 600 nm was greatly enhanced.

  16. Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles.

    PubMed

    Ma, Hui; Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan; Shi, Xiangyang

    2012-04-15

    Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants. PMID:22138171

  17. Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles.

    PubMed

    Ma, Hui; Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan; Shi, Xiangyang

    2012-04-15

    Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants.

  18. Salt flux synthesis of single and bimetallic carbide nanowires

    NASA Astrophysics Data System (ADS)

    Leonard, Brian M.; Waetzig, Gregory R.; Clouser, Dale A.; Schmuecker, Samantha M.; Harris, Daniel P.; Stacy, John M.; Duffee, Kyle D.; Wan, Cheng

    2016-07-01

    Metal carbide compounds have a broad range of interesting properties and are some of the hardest and highest melting point compounds known. However, their high melting points force very high reaction temperatures and thus limit the formation of high surface area nanomaterials. To avoid the extreme synthesis temperatures commonly associated with these materials, a new salt flux technique has been employed to reduce reaction temperatures and form these materials in the nanometer regime. Additionally, the use of multiwall carbon nanotubes as a reactant further reduces the diffusion distance and provides a template for the final carbide materials. The metal carbide compounds produced through this low temperature salt flux technique maintain the nanowire morphology of the carbon nanotubes but increase in size to ˜15-20 nm diameter due to the incorporation of metal in the carbon lattice. These nano-carbides not only have nanowire like shape but also have much higher surface areas than traditionally prepared metal carbides. Finally, bimetallic carbides with composition control can be produced with this method by simply using two metal precursors in the reaction. This method provides the ability to produce nano sized metal carbide materials with size, morphology, and composition control and will allow for these compounds to be synthesized and studied in a whole new size and temperature regime.

  19. Patched bimetallic surfaces are active catalysts for ammonia decomposition

    DOE PAGES

    Guo, Wei; Vlachos, Dionisios G.

    2015-10-07

    In this study, ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material’s structure. Core–shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core–shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-Hmore » bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.« less

  20. Fundamental studies of supported bimetallic catalysts by NMR spectroscopy

    SciTech Connect

    Savargaonkar, N.

    1996-10-17

    Various hydrogenation reactions on transition metals are important commercially whereas certain hydrogenolysis reactions are useful from fundamental point of view. Understanding the hydrogen mobility and kinetics of adsorption-desorption of hydrogen is important in understanding the mechanisms of such reactions involving hydrogen. The kinetics of hydrogen chemisorption was studied by means of selective excitation NMR on silica supported Pt, Rh and Pt-Rh catalysts. The activation energy of hydrogen desorption was found to be lower on silica supported Pt catalysts as compared to Rh and Pt-Rh catalysts. It was found that the rates of hydrogen adsorption and desorption on Pt-Rh catalyst were similar to those on Rh catalyst and much higher as compared to Pt catalyst. The Ru-Ag bimetallic system is much simpler to study than the Pt-Rh system and serves as a model system to characterize more complicated systems such as the K/Ru system. Ag was found to decrease the amounts of adsorbed hydrogen and the hydrogen-to-ruthenium stoichiometry. Ag reduced the populations of states with low and intermediate binding energies of hydrogen on silica supported Ru catalyst. The rates of hydrogen adsorption and desorption were also lower on silica supported Ru-Ag catalyst as compared to Ru catalyst. This report contains introductory information, the literature review, general conclusions, and four appendices. An additional four chapters and one appendix have been processed separately for inclusion on the data base.

  1. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction

    SciTech Connect

    Chunshan, Song; Kirby, S.; Schmidt, E.

    1995-12-31

    The objective of this project is to explore bimetallic dispersed catalysts for more efficient coal liquefaction. Coal liquefaction involves cleavage of methylene, dimethylene and ether bridges connecting various aromatic units and the reactions of various oxygen functional groups. This paper describes recent results on (1) hydrodeoxygenation of O-containing polycyclic model compounds using novel organometallic catalyst precursors; and (2) activity and selectivity of dispersed Fe catalysts from organometallic and inorganic precursors for hydrocracking of 4-(1-naphthylmethyl) bibenzyl. The results showed that some iron containing catalysts have higher activity in the sulfur-free form, contrary to conventional wisdom. Adding sulfur to Fe precursors with Cp-ligands decreased the activity of the resulting catalyst. This is in distinct contrast to the cases with iron pentacarbonyl and superfine Fe{sub 2}O{sub 3}, where S addition increased their catalytic activity substantially. A positive correlation between sulfur addition and increased activity can be seen, but a reversed trend between Fe cluster size and hydrocracking conversion could be observed, for carbonyl-type Fe precursors. It is apparent that the activity and selectivity of Fe catalysts for NMBB conversion depends strongly on both the type of ligand environment, the oxidation state and the number of intermetal bonds in the molecular precursor.

  2. Sulfentrazone dechlorination by iron-nickel bimetallic nanoparticles.

    PubMed

    Nascimento, Mayra A; Lopes, Renata P; Cruz, Jean C; Silva, Antônio A; Lima, Claudio F

    2016-04-01

    The sulfentrazone dechlorination using bimetallic nanoparticles of Fe/Ni was studied. Different variables that could influence the sulfentrazone conversion were investigated, such as nitrogen atmosphere, pH and dosage of the nanoparticles and initial concentration of sulfentrazone. The best results were obtained using controlled pH (pH 4.0) and 1.0 g L(-1) of nanomaterials, resulting in 100 % conversion in only 30 min. Kinetic studies were also conducted, evaluating the influence of different nanoparticle dosages (1.0 to 4.0 g L(-1)), system temperatures (20 to 35 °C) and nickel levels in the composition of the nanomaterials (0.025 to 0.10 gNi/gFe). The mechanism of sulfentrazone conversion has changed due a direct reduction on the catalytic activity sites and indirect reduction by atomic hydrogen. Both mechanisms have followed pseudo-first order models. The conversion rate improved when the dosage of the nanomaterials, system temperature and nickel content in the composition of the nanocomposites were increased. Finally, the conversion products were elucidated by mass spectrometry and toxicity assays were performed using Daphnia Similis. The results showed that the dechlorination product is less toxic than sulfentrazone. PMID:26802513

  3. Mono- and bimetallic zwitterionic chromium(0) and tungsten(0) allenyls.

    PubMed

    Giner, Elena A; Santiago, Alicia; Gómez-Gallego, Mar; Ramírez de Arellano, Carmen; Poulten, Rebecca C; Whittlesey, Michael K; Sierra, Miguel A

    2015-06-01

    A series of stable chiral (racemic), formally neutral, zwitterionic mono- and bimetallic M(CO)5[C(OEt)═C═CR(NHC)] (M = Cr, W) σ-allenyls are ready available by the addition of N-heterocyclic carbenes (NHCs) to Cr(0) and W(0) alkynyl Fischer carbene complexes. Different classes of NHCs, (e.g., 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene, and their six- and seven-membered analogues and 1,3-bis(dimethyl)imidazol-2-ylidene) were employed as nucleophiles in these C-C bond-forming reactions yielding the novel complexes in essentially quantitative yields. A systematic experimental and computational study of the electronic properties of the Cr- and W-allenyls shows that their UV-vis spectra are directly influenced by the structure of the heterocyclic moiety derived from the NHC (ring size, substituents on the N atoms) and by the nature of the metal fragment (Cr/W). The electron-releasing nature of these complexes allows them to participate in electron-transfer reactions in the ground state, leading to a type of charged α,β-unsaturated Fischer carbenes that incorporate an NHC fragment in their structure.

  4. Designing Bimetallic Co-Catalysts: A Party of Two.

    PubMed

    Aronovitch, Eran; Kalisman, Philip; Mangel, Shai; Houben, Lothar; Amirav, Lilac; Bar-Sadan, Maya

    2015-09-17

    The enhanced catalytic properties of bimetallic particles has made them the focus of extensive research. We compare the photocatalytic activity for hydrogen production of core-shell structures of Au@Pd and Au@(Au/Pd alloy) on seeded rods of CdSe@CdS and show that Au@alloy was superior toward hydrogen production. Our finding reveals that the promotion effects of Au in Pd originate both from the alteration of the electronic structure by the Au core as well as by the atomic rearrangement of the surface. Long-term monitoring of the activity of the photocatalysts offered insights into the dynamic processes during the illumination showing that the tip morphology influenced the stability of the hybrid structures. The Au core served as a physical barrier, protecting the CdS rod against cation exchange reactions with the Pd. The coupling of these factors to achieve synergistic effects is therefore a prime aspect in the rational design of efficient cocatalysts. PMID:26722753

  5. Salt flux synthesis of single and bimetallic carbide nanowires

    NASA Astrophysics Data System (ADS)

    Leonard, Brian M.; Waetzig, Gregory R.; Clouser, Dale A.; Schmuecker, Samantha M.; Harris, Daniel P.; Stacy, John M.; Duffee, Kyle D.; Wan, Cheng

    2016-07-01

    Metal carbide compounds have a broad range of interesting properties and are some of the hardest and highest melting point compounds known. However, their high melting points force very high reaction temperatures and thus limit the formation of high surface area nanomaterials. To avoid the extreme synthesis temperatures commonly associated with these materials, a new salt flux technique has been employed to reduce reaction temperatures and form these materials in the nanometer regime. Additionally, the use of multiwall carbon nanotubes as a reactant further reduces the diffusion distance and provides a template for the final carbide materials. The metal carbide compounds produced through this low temperature salt flux technique maintain the nanowire morphology of the carbon nanotubes but increase in size to ∼15–20 nm diameter due to the incorporation of metal in the carbon lattice. These nano-carbides not only have nanowire like shape but also have much higher surface areas than traditionally prepared metal carbides. Finally, bimetallic carbides with composition control can be produced with this method by simply using two metal precursors in the reaction. This method provides the ability to produce nano sized metal carbide materials with size, morphology, and composition control and will allow for these compounds to be synthesized and studied in a whole new size and temperature regime.

  6. Field assessment of nanoscale bimetallic particles for groundwater treatment.

    PubMed

    Elliott, D W; Zhang, W X

    2001-12-15

    A field demonstration was performed in which nanoscale bimetallic (Fe/Pd) particles were gravity-fed into groundwater contaminated bytrichloroethene and other chlorinated aliphatic hydrocarbons at a manufacturing site. With diameters on the order of 100-200 nm, the nanoparticles are uniquely suited to rapidly degrade redox-amenable contaminants and for optimal subsurface delivery and dispersion. Approximately 1.7 kg of the nanoparticles was fed into the test area over a 2-day period, resulting in minimal clogging of the injection well. The test area was located within a well-characterized region of the contaminant plume and included an injection well and three piezometer couplets spaced 1.5 m apart. Despite the low nanoparticle dosage, trichloroethene reduction efficiencies of up to 96% were observed over a 4-week monitoring period with the highest values observed at the injection well and adjacent piezometers. Data from the field assessment were consistent with the results of pre-injection laboratory studies, which showed rapid dechlorination of target chlorinated compounds accompanied by a sharp decrease of standard oxidation potential and an increase in pH. PMID:11775172

  7. Vibrational spectroscopic studies of adsorbates on bimetallic surfaces. Doctoral thesis

    SciTech Connect

    Kuhn, W.K.

    1992-12-01

    In this work, well-defined bimetallic surfaces have been studied using carbon monoxide adsorption in conjunction with infrared reflection absorption spectroscopy (IRAS). These studies have indicated that for CO adsorbed on Cu overlayers, the bond between the CO and the Cu adatoms is comprised of both pi-back-donation and polarization interaction components. The sum of the contributions from these effects determines the observed bond strength with the observed CO stretching frequency being determined by the relative contributions of the components. In addition, it was determined that IR spectra of adsorbed CO show a remarkable sensitivity to surface structure. Three-dimensional Cu clusters, well-ordered two dimensional Cu islands and isolated Cu atoms are distinctively characterized by their CO IR peaks. In addition, both disorder-order and order-order transitions are observed for the metal overlayers on the single crystal metal substrates. It was also observed that localized segregation and ordering of mixed Co and S overlayers on a Mo(110) substrate occurs upon annealing.

  8. One-step synthesis of dispersed bimetallic carbides and nitrides from transition metals hexamethylenetetramine complexes

    SciTech Connect

    Chouzier, Sandra; Afanasiev, Pavel . E-mail: Pavel.Afanasiev@catalyse.cnrs.fr; Vrinat, Michel; Cseri, Tivadar; Roy-Auberger, Magalie

    2006-11-15

    Bimetallic nitrides and carbides Co(Ni)-Mo were obtained from the decomposition of transition metals complexes with hexamethylenetetramine (HMTA) under inert atmosphere. The precursor complexes were prepared by means of aqueous precipitation of ammonium molybdate with cobalt nitrate or nickel nitrate and HMTA. During the decomposition, HMTA acts at once as a reducing agent and as a source of carbon and nitrogen. The precursor's composition and the decomposition conditions are the key parameters to influence the nature of the obtained phases. The method developed provides a simple one-step way to highly divided bimetallic nitrides and carbides. -- Graphical abstract: Bimetallic nitrides and carbides Co(Ni)-Mo were obtained from the decomposition of metals complexes with hexamethylenetetramine (HMTA) under inert atmosphere. During the decomposition, HMTA acts at once as a reducing agent and as a source of carbon and nitrogen. The method provides a simple one-step way to highly divided nitrides and carbides. Display Omitted.

  9. Bimetallic Metal-Organic Frameworks for Controlled Catalytic Graphitization of Nanoporous Carbons

    PubMed Central

    Tang, Jing; Salunkhe, Rahul R.; Zhang, Huabin; Malgras, Victor; Ahamad, Tansir; Alshehri, Saad M.; Kobayashi, Naoya; Tominaka, Satoshi; Ide, Yusuke; Kim, Jung Ho; Yamauchi, Yusuke

    2016-01-01

    Single metal-organic frameworks (MOFs), constructed from the coordination between one-fold metal ions and organic linkers, show limited functionalities when used as precursors for nanoporous carbon materials. Herein, we propose to merge the advantages of zinc and cobalt metals ions into one single MOF crystal (i.e., bimetallic MOFs). The organic linkers that coordinate with cobalt ions tend to yield graphitic carbons after carbonization, unlike those bridging with zinc ions, due to the controlled catalytic graphitization by the cobalt nanoparticles. In this work, we demonstrate a feasible method to achieve nanoporous carbon materials with tailored properties, including specific surface area, pore size distribution, degree of graphitization, and content of heteroatoms. The bimetallic-MOF-derived nanoporous carbon are systematically characterized, highlighting the importance of precisely controlling the properties of the carbon materials. This can be done by finely tuning the components in the bimetallic MOF precursors, and thus designing optimal carbon materials for specific applications. PMID:27471193

  10. Design and performance benchmark of various architectures of a piezoelectric bimetallic strip heat engine

    NASA Astrophysics Data System (ADS)

    Boughaleb, J.; Arnaud, A.; Monfray, S.; Cottinet, P. J.; Quenard, S.; Boeuf, F.; Guyomar, D.; Skotnicki, T.

    2016-06-01

    This paper deals with an investigation of a thermal energy harvester based on the coupling of a piezoelectric membrane and a bimetallic strip heat engine. The general working principle of the device consists of a double conversion mechanism: the thermal energy is first converted into mechanical energy by means of a bimetallic strip, then the mechanical energy is converted into electricity with a piezoelectric membrane. This paper deals with the study and optimization of the harvester's design. First, the piezoelectric membrane configuration is studied to find the most efficient way to convert mechanical energy into electricity. A benchmark of various piezoelectric materials is then presented to point out the most efficient materials. Finally, our study focuses on the bimetallic strip's properties: the effect of its dimensions of its thermal hysteresis on the harvester's performances are studied and compared. Thanks to these different steps, we were able to point out the best configuration to convert efficiently thermal heat flux into electricity.

  11. Description of the performances of a thermo-mechanical energy harvester using bimetallic beams

    NASA Astrophysics Data System (ADS)

    Arnaud, A.; Boughaleb, J.; Monfray, S.; Boeuf, F.; Cugat, O.; Skotnicki, T.

    2016-06-01

    Many recent researches have been focused on the development of thermal energy harvesters using thermo-mechanical or thermo-electrical coupling phenomena associated to a first-order thermodynamic transition. In the case of the bimetallic strip heat engine, the exploitation of the thermo-mechanical instability of bimetallic membranes placed in a thermal gradient enables to convert heat into kinetic energy. This paper is a contribution to the modeling and the comprehension of these heat engines. By restraining the study to the simply-supported bimetallic beams and using a Ritz approximation of the beam shape, this paper aims to give an analytical solution to the first mode of the composite beams and then to evaluate the efficiency of the harvesters exploiting these kinds of instability.

  12. Synthesis of supported bimetallic nanoparticles with controlled size and composition distributions for active site elucidation

    SciTech Connect

    Hakim, Sikander H.; Sener, Canan; Alba Rubio, Ana C.; Gostanian, Thomas M.; O'neill, Brandon J; Ribeiro, Fabio H.; Miller, Jeffrey T.; Dumesic, James A

    2015-08-01

    Elucidation of active sites in supported bimetallic catalysts is complicated by the high level of dispersity in the nanoparticle size and composition that is inherent in conventional methods of catalyst preparation. We present a synthesis strategy that leads to highly dispersed, bimetallic nanoparticles with uniform particle size and composition by means of controlled surface reactions. We demonstrate the synthesis of three systems, RhMo, PtMo, and RhRe, consisting of a highly reducible metal with an oxophilic promoter. These catalysts are characterized by FTIR, CO chemisorption, STEM/EDS, TPR, and XAS analysis. The catalytic properties of these bimetallic nanoparticles were probed for the selective CO hydrogenolysis of (hydroxymethyl)tetrahydropyran to produce 1,6 hexanediol. Based on the characterization results and reactivity trends, the active sites in the hydrogenolysis reaction are identified to be small ensembles of the more noble metal (Rh, Pt) adjacent to highly reduced moieties of the more oxophilic metal (Mo, Re).

  13. Bimetallic Metal-Organic Frameworks for Controlled Catalytic Graphitization of Nanoporous Carbons.

    PubMed

    Tang, Jing; Salunkhe, Rahul R; Zhang, Huabin; Malgras, Victor; Ahamad, Tansir; Alshehri, Saad M; Kobayashi, Naoya; Tominaka, Satoshi; Ide, Yusuke; Kim, Jung Ho; Yamauchi, Yusuke

    2016-01-01

    Single metal-organic frameworks (MOFs), constructed from the coordination between one-fold metal ions and organic linkers, show limited functionalities when used as precursors for nanoporous carbon materials. Herein, we propose to merge the advantages of zinc and cobalt metals ions into one single MOF crystal (i.e., bimetallic MOFs). The organic linkers that coordinate with cobalt ions tend to yield graphitic carbons after carbonization, unlike those bridging with zinc ions, due to the controlled catalytic graphitization by the cobalt nanoparticles. In this work, we demonstrate a feasible method to achieve nanoporous carbon materials with tailored properties, including specific surface area, pore size distribution, degree of graphitization, and content of heteroatoms. The bimetallic-MOF-derived nanoporous carbon are systematically characterized, highlighting the importance of precisely controlling the properties of the carbon materials. This can be done by finely tuning the components in the bimetallic MOF precursors, and thus designing optimal carbon materials for specific applications. PMID:27471193

  14. Stellated Ag-Pt bimetallic nanoparticles: An effective platform for catalytic activity tuning

    PubMed Central

    Liu, Hui; Ye, Feng; Yao, Qiaofeng; Cao, Hongbin; Xie, Jianping; Lee, Jim Yang; Yang, Jun

    2014-01-01

    The usefulness of Pt-based nanomaterials for catalysis can be greatly enhanced by coupling morphology engineering to the strategic presence of a second or even third metal. Here we demonstrate the design and preparation of stellated Ag-Pt bimetallic nanoparticles where significant activity difference between the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR) may be realized by relegating Ag to the core or by hollowing out the core. In particular the stellated Pt surface, with an abundance of steps, edges, corner atoms, and {111} facets, is highly effective for the ORR but is ineffective for MOR. MOR activity is only observed in the presence of a Ag core through electronic coupling to the stellated Pt shell. The bimetallic Ag-Pt stellates therefore demonstrate the feasibility of tuning a Pt surface for two very different structure sensitive catalytic reactions. Stellated bimetallics may therefore be an effective platform for highly tunable catalyst designs. PMID:24495979

  15. Bimetallic Metal-Organic Frameworks for Controlled Catalytic Graphitization of Nanoporous Carbons

    NASA Astrophysics Data System (ADS)

    Tang, Jing; Salunkhe, Rahul R.; Zhang, Huabin; Malgras, Victor; Ahamad, Tansir; Alshehri, Saad M.; Kobayashi, Naoya; Tominaka, Satoshi; Ide, Yusuke; Kim, Jung Ho; Yamauchi, Yusuke

    2016-07-01

    Single metal-organic frameworks (MOFs), constructed from the coordination between one-fold metal ions and organic linkers, show limited functionalities when used as precursors for nanoporous carbon materials. Herein, we propose to merge the advantages of zinc and cobalt metals ions into one single MOF crystal (i.e., bimetallic MOFs). The organic linkers that coordinate with cobalt ions tend to yield graphitic carbons after carbonization, unlike those bridging with zinc ions, due to the controlled catalytic graphitization by the cobalt nanoparticles. In this work, we demonstrate a feasible method to achieve nanoporous carbon materials with tailored properties, including specific surface area, pore size distribution, degree of graphitization, and content of heteroatoms. The bimetallic-MOF-derived nanoporous carbon are systematically characterized, highlighting the importance of precisely controlling the properties of the carbon materials. This can be done by finely tuning the components in the bimetallic MOF precursors, and thus designing optimal carbon materials for specific applications.

  16. (Plasmonic Metal Core)/(Semiconductor Shell) Nanostructures

    NASA Astrophysics Data System (ADS)

    Fang, Caihong

    shape is maintained throughout the sulfidation process, with the edge length being increased gradually. TiO2 is one of the most important semiconductors that are employed in light-harvesting applications. It has been extensively studied for a variety of applications by virtue of its low toxicity, biological compatibility, chemical and thermal stability, resistance to photocorrosion, and relative abundance. However, the photocatalytic activity of TiO2 is limited to the UV region because of its wide band gap, which limits its applications in light harvesting. Although (Au core)/(TiO2 shell) nanostructures can improve the photocatalytic activities of TiO2 in visible light, it has only been demonstrated in a few experiments and has been limited with Au nanospheres. Compared with Au nanospheres, Au nanorods offer more attractive plasmonic features, including stronger electric field enhancements and synthetically tunable longitudinal plasmon wavelengths over the visible to near-infrared region. The coating of Au nanorod therefore can largely improve light harvesting capability of TiO2. In this thesis, I developed a facile and versatile method for the preparation of (Au nanocrystal core)/(TiO2 shell) nanostructures by using a Ti(III) compound as the titania precursor. By employing Au nanorods with different sizes and varying the shell thickness, the plasmonic bands of the core/shell nanostructures can be tailored. TiO2 can also be grown on other monometallic and bimetallic Pd, Pt, Au nanocrystals. As a proof-of-concept application, (Au nanorod core)/(TiO2 shell) nanostructures were utilized in dye-sensitized solar cells to function as a scattering layer. The resultant solar cells exhibited higher power conversion efficiencies with a thinner thickness compared to the traditional TiO 2 solar cells. In addition, I also examined the property of plasmon-enhanced reactive oxygen species generation. Moreover, the TiO2 shell with a high refractive index can efficiently couple with the

  17. INTERACTION OF SULPHUR WITH BIMETALLIC SURFACES: EFFECTS OF STRUCTURAL, ELECTRONIC AND CHEMICAL PROPERTIES.

    SciTech Connect

    RODRIGUEZ,J.A.; HRBEK,J.

    2001-10-04

    In recent years, several new interesting phenomena have been discovered when studying the interaction of sulphur with bimetallic surfaces using the modern techniques of surface science. Very small amounts of sulphur can induce dramatic changes in the morphology of bimetallic surfaces. The electronic perturbations associated with the formation of a heteronuclear metal-metal bond affect the reactivity of the bonded metals toward sulphur. This can be a very important issue to consider when trying to minimize the negative effects of sulphur poisoning or dealing with the design of desulfurization catalysts.

  18. Structure analysis of bimetallic Co-Au nanoparticles formed by sequential ion implantation

    NASA Astrophysics Data System (ADS)

    Chen, Hua-jian; Wang, Yu-hua; Zhang, Xiao-jian; Song, Shu-peng; chen, Hong; Zhang, Ke; Xiong, Zu-zhao; Ji, Ling-ling; Dai, Hou-mei; Wang, Deng-jing; Lu, Jian-duo; Wang, Ru-wu; Zheng, Li-rong

    2016-08-01

    Co-Au alloy Metallic nanoparticles (MNPs) are formed by sequential ion implantation of Co and Au into silica glass at room temperature. The ion ranges of Au ions implantation process have been displayed to show the ion distribution. We have used the atomic force microscopy (AFM) and transmission electron microscopy (TEM) to investigate the formation of bimetallic nanoparticles. The extended X-ray absorption fine structure (EXAFS) has been used to study the local structural information of bimetallic nanoparticles. With the increase of Au ion implantation, the local environments of Co ions are changed enormously. Hence, three oscillations, respectively, Co-O, Co-Co and Co-Au coordination are determined.

  19. Measuring Strong Nanostructures

    ScienceCinema

    Andy Minor

    2016-07-12

    Andy Minor of Berkeley Lab's National Center for Electron Microscopy explains measuring stress and strain on nanostructures with the In Situ Microscope. More information: http://newscenter.lbl.gov/press-relea...

  20. Measuring Strong Nanostructures

    SciTech Connect

    Andy Minor

    2008-10-16

    Andy Minor of Berkeley Lab's National Center for Electron Microscopy explains measuring stress and strain on nanostructures with the In Situ Microscope. More information: http://newscenter.lbl.gov/press-relea...

  1. Bioinspired chemistry: Rewiring nanostructures

    NASA Astrophysics Data System (ADS)

    Ulijn, Rein V.; Caponi, Pier-Francesco

    2010-07-01

    The cell's dynamic skeleton, a tightly regulated network of protein fibres, continues to provide inspiration for the design of synthetic nanostructures. Genetic engineering has now been used to encode non-biological functionality within these structures.

  2. Structure and properties of bimetallic titanium and vanadium oxide clusters.

    PubMed

    Helmich, Benjamin; Sierka, Marek; Döbler, Jens; Sauer, Joachim

    2014-05-14

    By employing a genetic algorithm together with density functional theory (B3LYP), we investigate the most stable minimum structures of several bimetallic titanium and vanadium oxide clusters that contain four metal atoms. The following compositions are studied: VnTin-4O10(-) (n = 1-4), (TiO2)VOn(-) (n = 1-4), and (TiO2)VOn(+) (n = 1-3). Apart from (TiO2)3VO(-), vanadium oxo groups are always part of the most stable minimum structures when vanadium is present. Anti-ferromagnetic coupling lowers the energy substantially if spin centers are located at neighbored metal atoms rather than at distant oxygen radical sites. Vanadium-rich or oxygen-poor compositions prefer symmetric adamantane-like cage structures, some of which have already been proposed in a previous study. In contrast, vanadium-poor and oxygen-rich compositions show versatile structural motifs that cannot be intuitively derived from the symmetric cage motif. Particularly, for Ti4O10(-) there are several non-symmetric and distorted cages that have an up to 68 kJ mol(-1) lower energy than the symmetric adamantane-like cage structure. Nevertheless, for the adamantane-like cage the simulated infra-red spectrum (within the harmonic approximation) agrees best with the experimental vibrational spectrum. The oxidative power of the (TiO2)3VO3(-) and (TiO2)3VO2(+) clusters as measured by the energy of removing 1/2 O2 (297 and 227 kJ mol(-1), respectively) is less than that of the pure vanadium oxide clusters (V2O5)VO3(-) and (V2O5)VO2(+) (283 and 165 kJ mol(-1), respectively).

  3. Removal of arsenic (V) from water using hierarchical flower-shaped AlOOH/Fe micro/nanostructures

    NASA Astrophysics Data System (ADS)

    Bakina, O. V.; Glazkova, E. A.; Svarovskaya, N. V.; Berenda, A. V.; Lozhkomoev, A. S.; Lerner, M. I.

    2015-10-01

    Hierarchical AlOOH/Fe micro/nanostructures with flower-shaped morphology were fabricated by the reaction of Al/Fe nanoparticles with water. Al/Fe bimetallic nanoparticles have been obtained using the method of simultaneous electrical explosion of metal pairs in a nitrogen atmosphere. The nanoparticles are chemically active and interact with water at 60°C forming the flower-shaped hierarchical pore structures with a high specific surface area. Al/Fe product transformations are presented by the flower-shaped pseudoboehmite surrounded by the lamellar structures enriched with ferric oxides. Flower-shaped AlOOH/Fe micro/nanostructure with flower-shaped morphology is found to serve as an effective adsorbent medium to remove As(V) from water. The adsorption capacity was 43 mg/g (pH = 6.7).

  4. ELECTRONIC AND CHEMICAL PROPERTIES OF PD IN BIMETALLIC SYSTEMS: HOW MUCH DO WE KNOW ABOUT HETERONUCLEAR METAL-METAL BONDING?

    SciTech Connect

    RODRIGUEZ,J.A.

    2001-09-27

    The experimental and theoretical studies described above illustrate the complex nature of the heteronuclear metal-metal bond. In many cases, bimetallic bonding induces a significant redistribution of charge around the bonded metals. This redistribution of charge is usually linked to the strength of the bimetallic bond, affects the position of the core and valence levels of the metals, and can determine the chemical reactivity of the system under study. New concepts are emerging [22,23,34,36] and eventually the coupling of experiment and theory can be useful for designing more efficient bimetallic catalysts [98,106,107].

  5. PD/MG BIMETALLIC CORROSION SYSTEMS FOR DECHLORINATION OF PCB CONTAMINATED MATRICES

    EPA Science Inventory

    Polychlorinated biphenyls (PCBs), a family of 209 compounds manufactured till mid70's, are toxic pollutants that persist in the environment. Enhanced corrosion of an active metal combined with catalytic hydrogenation properties of Pd in bimetallic cells can effectively reduce PCB...

  6. The effect of the surface composition of Ru-Pt bimetallic catalysts for methanol oxidation

    DOE PAGES

    Garrick, Taylor R.; Diao, Weijian; Tengco, John M.; Stach, Eric A.; Senanayake, Sanjaya D.; Chen, Donna A.; Monnier, John R.; Weidner, John W.

    2016-02-23

    Here, a series of Ru-Pt bimetallic catalysts prepared by the electroless deposition of controlled and variable amounts of Ru on the Pt surface of a commercially-available 20 wt% Pt/C catalyst has been characterized and evaluated for the oxidation of methanol. The activity of each Ru-Pt catalyst was determined as a function of surface composition via cyclic voltammetry. For the Ru-Pt bimetallic catalysts, activity passed through a maximum at approximately 50% monodisperse Ru surface coverage. However, due to the monolayer coverage of Ru on Pt, the amount of metal in the catalyst is minimized compared to a bulk 1:1 atomic ratiomore » of Ru:Pt seen in commercial bimetallic catalysts. Chemisorption and temperature programmed reduction experiments confirmed that the surface had characteristics of a true bimetallic catalyst. On a mass of Pt basis, the activity of this composition for methanol oxidation was 7 times higher than pure Pt and 3.5 times higher than a commercial catalyst with a 1:1 Pt:Ru bulk atomic ratio.« less

  7. Fundamental studies of hydrogen interaction with supported meta and bimetallic catalysts

    SciTech Connect

    Bhatia, S.

    1993-12-07

    The thesis is divided into 3 parts: interaction of H with silica supported Ru catalysts (high pressure in situ NMR), in situ NMR study of H interaction with supported Ru-group IB bimetallic catalysts, and in-situ NMR study of H effects on silica-supported Pt, Rh and Ru catalysts.

  8. ENHANCED CORRISION-BASED PD/MG BIMETALLIC SYSTEMS FOR DECHLORINATION OF PCBS

    EPA Science Inventory

    Polychlorinated biphenyls (PCBs) are toxic pollutants notorious for their aquatic and sedimentary prevalence and recalcitrant nature. Bimetallic systems like Pd/Fe have been widely studied for degrading them. Mg, with oxidation potential higher than Fe, has been reported to dechl...

  9. Theoretical studies of the work functions of Pd-based bimetallic surfaces

    SciTech Connect

    Ding, Zhao-Bin; Wu, Feng; Wang, Yue-Chao; Jiang, Hong

    2015-06-07

    Work functions of Pd-based bimetallic surfaces, including mainly M/Pd(111), Pd/M, and Pd/M/Pd(111) (M = 4d transition metals, Cu, Au, and Pt), are studied using density functional theory. We find that the work function of these bimetallic surfaces is significantly different from that of parent metals. Careful analysis based on Bader charges and electron density difference indicates that the variation of the work function in bimetallic surfaces can be mainly attributed to two factors: (1) charge transfer between the two different metals as a result of their different intrinsic electronegativity, and (2) the charge redistribution induced by chemical bonding between the top two layers. The first factor can be related to the contact potential, i.e., the work function difference between two metals in direct contact, and the second factor can be well characterized by the change in the charge spilling out into vacuum. We also find that the variation in the work functions of Pd/M/Pd(111) surfaces correlates very well with the variation of the d-band center of the surface Pd atom. The findings in this work can be used to provide general guidelines to design new bimetallic surfaces with desired electronic properties.

  10. Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors.

    PubMed

    Ahmed, Suzanne; Wang, Wei; Bai, Lanjun; Gentekos, Dillon T; Hoyos, Mauricio; Mallouk, Thomas E

    2016-04-26

    Bimetallic nanorods are propelled without chemical fuels in megahertz (MHz) acoustic fields, and exhibit similar behaviors to single-metal rods, including autonomous axial propulsion and organization into spinning chains. Shape asymmetry determines the direction of axial movement of bimetallic rods when there is a small difference in density between the two metals. Movement toward the concave end of these rods is inconsistent with a scattering mechanism that we proposed earlier for acoustic propulsion, but is consistent with an acoustic streaming model developed more recently by Nadal and Lauga ( Phys. Fluids 2014 , 26 , 082001 ). Longer rods were slower at constant power, and their speed was proportional to the square of the power density, in agreement with the acoustic streaming model. The streaming model was further supported by a correlation between the disassembly of spinning chains of rods and a sharp decrease in the axial speed of autonomously moving motors within the levitation plane of the cylindrical acoustic cell. However, with bimetallic rods containing metals of different densities, a consistent polarity of motion was observed with the lighter metal end leading. Speed comparisons between single-metal rods of different densities showed that those of lower density are propelled faster. So far, these density effects are not explained in the streaming model. The directionality of bimetallic rods in acoustic fields is intriguing and offers some new possibilities for designing motors in which shape, material, and chemical asymmetry might be combined for enhanced functionality. PMID:26991933

  11. A Systematic Investigation of p-Nitrophenol Reduction by Bimetallic Dendrimer Encapsulated Nanoparticles

    PubMed Central

    2013-01-01

    We demonstrate that the reduction of p-nitrophenol to p-aminophenol by NaBH4 is catalyzed by both monometallic and bimetallic nanoparticles (NPs). We also demonstrate a straightforward and precise method for the synthesis of bimetallic nanoparticles using poly(amido)amine dendrimers. The resulting dendrimer encapsulated nanoparticles (DENs) are monodisperse, and the size distribution does not vary with different elemental combinations. Random alloys of Pt/Cu, Pd/Cu, Pd/Au, Pt/Au, and Au/Cu DENs were synthesized and evaluated as catalysts for p-nitrophenol reduction. These combinations are chosen in order to selectively tune the binding energy of the p-nitrophenol adsorbate to the nanoparticle surface. Following the Brønsted–Evans–Polanyi (BEP) relation, we show that the binding energy can reasonably predict the reaction rates of p-nitrophenol reduction. We demonstrate that the measured reaction rate constants of the bimetallic DENs is not always a simple average of the properties of the constituent metals. In particular, DENs containing metals with similar lattice constants produce a binding energy close to the average of the two constituents, whereas DENs containing metals with a lattice mismatch show a bimodal distribution of binding energies. Overall, in this work we present a uniform method for synthesizing pure and bimetallic DENs and demonstrate that their catalytic properties are dependent on the adsorbate’s binding energy. PMID:23616909

  12. Synthesis of bimetallic gold-silver alloy nanoclusters by simple mortar grinding.

    PubMed

    Murugadoss, Arumugam; Kai, Noriko; Sakurai, Hidehiro

    2012-02-21

    A macroscale quantity of bimetallic Au-Ag alloy nanoclusters was achieved through sequential reduction by simple mortar grinding. The chitosan biopolymer was used as both a stabilizing and reducing agent. These nanoclusters exhibit excellent catalytic activity toward the reduction of 4-nitrophenol.

  13. VAPOR PHASE MERCURY SORPTION BY ORGANIC SULFIDE MODIFIED BIMETALLIC IRON-COPPER NANOPARTICLE AGGREGATES

    EPA Science Inventory

    Novel organic sulfide modified bimetallic iron-copper nanoparticle aggregate sorbent materials have been synthesized for removing elemental mercury from vapor streams at elevated temperatures (120-140 °C). Silane based (disulfide silane and tetrasulfide silane) and alkyl sulfide ...

  14. Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors.

    PubMed

    Ahmed, Suzanne; Wang, Wei; Bai, Lanjun; Gentekos, Dillon T; Hoyos, Mauricio; Mallouk, Thomas E

    2016-04-26

    Bimetallic nanorods are propelled without chemical fuels in megahertz (MHz) acoustic fields, and exhibit similar behaviors to single-metal rods, including autonomous axial propulsion and organization into spinning chains. Shape asymmetry determines the direction of axial movement of bimetallic rods when there is a small difference in density between the two metals. Movement toward the concave end of these rods is inconsistent with a scattering mechanism that we proposed earlier for acoustic propulsion, but is consistent with an acoustic streaming model developed more recently by Nadal and Lauga ( Phys. Fluids 2014 , 26 , 082001 ). Longer rods were slower at constant power, and their speed was proportional to the square of the power density, in agreement with the acoustic streaming model. The streaming model was further supported by a correlation between the disassembly of spinning chains of rods and a sharp decrease in the axial speed of autonomously moving motors within the levitation plane of the cylindrical acoustic cell. However, with bimetallic rods containing metals of different densities, a consistent polarity of motion was observed with the lighter metal end leading. Speed comparisons between single-metal rods of different densities showed that those of lower density are propelled faster. So far, these density effects are not explained in the streaming model. The directionality of bimetallic rods in acoustic fields is intriguing and offers some new possibilities for designing motors in which shape, material, and chemical asymmetry might be combined for enhanced functionality.

  15. NOVEL SUPPORTED BIMETALLIC CARBIDE CATALYSTS FOR COPROCESSING OF COAL WITH WASTE METERIALS

    SciTech Connect

    S. Ted Oyama; David F. Cox; Chunshan Song; Fred Allen; Weilin Wang; Viviane Schwartz; Xinqin Wang; Jianli Yang

    2001-01-01

    The overall objectives of this project are to explore the potential of novel monometallic and bimetallic Mo-based carbide catalysts for heavy hydrocarbon coprocessing, and to understand the fundamental chemistry related to the reaction pathways of coprocessing and the role of the catalysts in the conversion of heavy hydrocarbon resources into liquid fuels based on the model compound reactions.

  16. Green synthesis of Fe0 and bimetallic Fe0 for oxidative catalysis and reduction applications

    EPA Science Inventory

    A single-step green approach to the synthesis of nanoscale zero valent iron (nZVI) and nanoscale bimetallic (Fe0/Pd) particles using tea (Camellia sinensis) polyphenols is described. The expedient reaction between polyphenols and ferric chloride (FeCl3) occurs within a minute at ...

  17. Chemistry of bimetallic linked cyclopentadienyl complexes: Progress report, 1 December 1986--30 November 1989

    SciTech Connect

    Schrock, R.R.

    1986-12-01

    Research continued on the chemistry and preparation of bimetallic cyclopentadienyl complexes containing up to two tungsten or one tungsten and a cobalt, rhodium, or ruthenium. The general method for preparation and analysis of polyenes is also discussed. 7 figs., 2 tabs. (CBS)

  18. Voltammetric surface dealloying of Pt bimetallic nanoparticles: an experimental and DFT computational analysis.

    PubMed

    Strasser, Peter; Koh, Shirlaine; Greeley, Jeff

    2008-07-01

    Voltammetric dealloying of bimetallic platinum-copper (Pt-Cu) alloys has been shown to be an effective strategy to modify the surface electrocatalytic reactivity of Pt bimetallic nanoparticles (S. Koh and P. Strasser, J. Am. Chem. Soc., 2007, 129, 12624). Using cyclic voltammetry and structural XRD studies, we systematically characterize the Pt-Cu precursor compounds as well as the early stages of the selective Cu surface dissolution (dealloying) process for Pt(25)Cu(75), Pt(50)Cu(50), and Pt(75)Cu(25) alloy nanoparticles annealed at both low and high temperature. We also assess the impact of the synthesis conditions on the electrocatalytic reactivity for the oxygen reduction reaction (ORR). To gain atomistic insight into the observed voltammetric profiles, we compare our experimental results with periodic DFT calculations of trends in the thermodynamics of surface Cu dissolution potentials from highly stepped and kinked Pt(854) single crystal surfaces. The modeling suggests a dependence of the electrochemical Cu dissolution potentials on the detailed atomic environment (coordination number, nature of coordinating atoms) of the bimetallic Pt-Cu surfaces. The DFT-predicted shifts in electrochemical Cu dissolution potentials are shown to qualitatively account for the observed voltammetric profiles during Cu dealloying. Our study suggests that metal-specific energetics have to be taken into account to explain the detailed dealloying behavior of bimetallic surfaces. PMID:18563228

  19. Non-precious bimetallic catalysts for selective dehydrogenation of an organic chemical hydride system.

    PubMed

    Al-ShaikhAli, Anaam H; Jedidi, Abdesslem; Cavallo, Luigi; Takanabe, Kazuhiro

    2015-08-21

    Methylcyclohexane (MCH)-toluene (TOL) chemical hydride cycles as hydrogen carrier systems are successful with the selective dehydrogenation of MCH to TOL, which has been achieved only using precious Pt-based catalysts. Herein, we report improved selectivity using non-precious metal nickel-based bimetallic catalysts, where the second metal occupies the unselective step sites.

  20. Structures of small Pd Pt bimetallic clusters by Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Cheng, Daojian; Huang, Shiping; Wang, Wenchuan

    2006-11-01

    Segregation phenomena of Pd-Pt bimetallic clusters with icosahedral and decahedral structures are investigated by using Monte Carlo method based on the second-moment approximation of the tight-binding (TB-SMA) potentials. The simulation results indicate that the Pd atoms generally lie on the surface of the smaller clusters. The three-shell onion-like structures are observed in 55-atom Pd-Pt bimetallic clusters, in which a single Pd atom is located in the center, and the Pt atoms are in the middle shell, while the Pd atoms are enriched on the surface. With the increase of Pd mole fraction in 55-atom Pd-Pt bimetallic clusters, the Pd atoms occupy the vertices of clusters first, then edge and center sites, and finally the interior shell. It is noticed that some decahedral structures can be transformed into the icosahedron-like structure at 300 and 500 K. Comparisons are made with previous experiments and theoretical studies of Pd-Pt bimetallic clusters.

  1. Nanostructures having high performance thermoelectric properties

    DOEpatents

    Yang, Peidong; Majumdar, Arunava; Hochbaum, Allon I; Chen, Renkun; Delgado, Raul Diaz

    2014-05-20

    The invention provides for a nanostructure, or an array of such nanostructures, each comprising a rough surface, and a doped or undoped semiconductor. The nanostructure is an one-dimensional (1-D) nanostructure, such a nanowire, or a two-dimensional (2-D) nanostructure. The nanostructure can be placed between two electrodes and used for thermoelectric power generation or thermoelectric cooling.

  2. Nanostructures having high performance thermoelectric properties

    DOEpatents

    Yang, Peidong; Majumdar, Arunava; Hochbaum, Allon I.; Chen, Renkun; Delgado, Raul Diaz

    2015-12-22

    The invention provides for a nanostructure, or an array of such nanostructures, each comprising a rough surface, and a doped or undoped semiconductor. The nanostructure is an one-dimensional (1-D) nanostructure, such a nanowire, or a two-dimensional (2-D) nanostructure. The nanostructure can be placed between two electrodes and used for thermoelectric power generation or thermoelectric cooling.

  3. Nanostructured materials in potentiometry.

    PubMed

    Düzgün, Ali; Zelada-Guillén, Gustavo A; Crespo, Gastón A; Macho, Santiago; Riu, Jordi; Rius, F Xavier

    2011-01-01

    Potentiometry is a very simple electrochemical technique with extraordinary analytical capabilities. It is also well known that nanostructured materials display properties which they do not show in the bulk phase. The combination of the two fields of potentiometry and nanomaterials is therefore a promising area of research and development. In this report, we explain the fundamentals of potentiometric devices that incorporate nanostructured materials and we highlight the advantages and drawbacks of combining nanomaterials and potentiometry. The paper provides an overview of the role of nanostructured materials in the two commonest potentiometric sensors: field-effect transistors and ion-selective electrodes. Additionally, we provide a few recent examples of new potentiometric sensors that are based on receptors immobilized directly onto the nanostructured material surface. Moreover, we summarize the use of potentiometry to analyze processes involving nanostructured materials and the prospects that the use of nanopores offer to potentiometry. Finally, we discuss several difficulties that currently hinder developments in the field and some future trends that will extend potentiometry into new analytical areas such as biology and medicine.

  4. Phytogenic silver, gold, and bimetallic nanoparticles as novel antitubercular agents

    PubMed Central

    Singh, Richa; Nawale, Laxman; Arkile, Manisha; Wadhwani, Sweety; Shedbalkar, Utkarsha; Chopade, Snehal; Sarkar, Dhiman; Chopade, Balu Ananda

    2016-01-01

    Purpose Multi- and extensively drug-resistant tuberculosis (TB) is a global threat to human health. It requires immediate action to seek new antitubercular compounds and devise alternate strategies. Nanomaterials, in the present scenario, have opened new avenues in medicine, diagnosis, and therapeutics. In view of this, the current study aims to determine the efficacy of phytogenic metal nanoparticles to inhibit mycobacteria. Methods Silver (AgNPs), gold (AuNPs), and gold–silver bimetallic (Au–AgNPs) nanoparticles synthesized from medicinal plants, such as Barleria prionitis, Plumbago zeylanica, and Syzygium cumini, were tested against Mycobacterium tuberculosis and M. bovis BCG. In vitro and ex vivo macrophage infection model assays were designed to determine minimum inhibitory concentration (MIC) and half maximal inhibitory concentration of nanoparticles. Microscopic analyses were carried out to demonstrate intracellular uptake of nanoparticles in macrophages. Besides this, biocompatibility, specificity, and selectivity of nanoparticles were also established with respect to human cell lines. Results Au–AgNPs exhibited highest antitubercular activity, with MIC of <2.56 μg/mL, followed by AgNPs. AuNPs did not show such activity at concentrations of up to 100 μg/mL. In vitro and ex vivo macrophage infection model assays revealed the inhibition of both active and dormant stage mycobacteria on exposure to Au–AgNPs. These nanoparticles were capable of entering macrophage cells and exhibited up to 45% cytotoxicity at 30 μg/mL (ten times MIC concentration) after 48 hours. Among these, Au–AgNPs synthesized from S. cumini were found to be more specific toward mycobacteria, with their selectivity index in the range of 94–108. Conclusion This is the first study to report the antimycobacterial activity of AuNPs, AgNPs, and Au–AgNPs synthesized from medicinal plants. Among these, Au–AgNPs from S. cumini showed profound efficiency, specificity, and

  5. Nanostructured materials for hydrogen storage

    DOEpatents

    Williamson, Andrew J.; Reboredo, Fernando A.

    2007-12-04

    A system for hydrogen storage comprising a porous nano-structured material with hydrogen absorbed on the surfaces of the porous nano-structured material. The system of hydrogen storage comprises absorbing hydrogen on the surfaces of a porous nano-structured semiconductor material.

  6. Synthesis of porphyrin nanostructures

    DOEpatents

    Fan, Hongyou; Bai, Feng

    2014-10-28

    The present disclosure generally relates to self-assembly methods for generating porphyrin nanostructures. For example, in one embodiment a method is provided that includes preparing a porphyrin solution and a surfactant solution. The porphyrin solution is then mixed with the surfactant solution at a concentration sufficient for confinement of the porphyrin molecules by the surfactant molecules. In some embodiments, the concentration of the surfactant is at or above its critical micelle concentration (CMC), which allows the surfactant to template the growth of the nanostructure over time. The size and morphology of the nanostructures may be affected by the type of porphyrin molecules used, the type of surfactant used, the concentration of the porphyrin and surfactant the pH of the mixture of the solutions, and the order of adding the reagents to the mixture, to name a few variables.

  7. Synthesis and structural characterization of an atom-precise bimetallic nanocluster, Ag4Ni2(DMSA)4.

    PubMed

    Biltek, Scott R; Mandal, Sukhendu; Sen, Ayusman; Reber, Arthur C; Pedicini, Anthony F; Khanna, Shiv N

    2013-01-01

    A bimetallic ligand-protected cluster, Ag(4)Ni(2)(DMSA)(4) (DMSA = meso-2,3-dimercaptosuccinic acid) was synthesized and characterized through electrospray ionization mass spectroscopy. Such bimetallic clusters involving a noble metal and a first-row transition metal have not been previously reported. Theoretical calculations revealed an octahedral structure with silver atoms occupying the corners of the square plane and the nickel atoms at the apexes. Close agreement between the predicted and observed spectroscopic features was found.

  8. Simulation of Semiconductor Nanostructures

    SciTech Connect

    Williamson, A J; Grossman, J C; Puzder, A; Benedict, L X; Galli, G

    2001-07-19

    The field of research into the optical properties of silicon nanostructures has seen enormous growth over the last decade. The discovery that silicon nanoparticles exhibit visible photoluminescence (PL) has led to new insights into the mechanisms responsible for such phenomena. The importance of understanding and controlling the PL properties of any silicon based material is of paramount interest to the optoelectronics industry where silicon nanoclusters could be embedded into existing silicon based circuitry. In this talk, we present a combination of quantum Monte Carlo and density functional approaches to the calculation of the electronic, structural, and optical properties of silicon nanostructures.

  9. Plasmonic nanostructures: artificial molecules.

    PubMed

    Wang, Hui; Brandl, Daniel W; Nordlander, Peter; Halas, Naomi J

    2007-01-01

    This Account describes a new paradigm for the relationship between the geometry of metallic nanostructures and their optical properties. While the interaction of light with metallic nanoparticles is determined by their collective electronic or plasmon response, a compelling analogy exists between plasmon resonances of metallic nanoparticles and wave functions of simple atoms and molecules. Based on this insight, an entire family of plasmonic nanostructures, artificial molecules, has been developed whose optical properties can be understood within this picture: nanoparticles (nanoshells, nanoeggs, nanomatryushkas, nanorice), multi-nanoparticle assemblies (dimers, trimers, quadrumers), and a nanoparticle-over-metallic film, an electromagnetic analog of the spinless Anderson model. PMID:17226945

  10. Plasmonics in nanostructures.

    PubMed

    Fang, Zheyu; Zhu, Xing

    2013-07-26

    Plasmonics has developed into one of the rapidly growing research topics for nanophotonics. With advanced nanofabrication techniques, a broad variety of nanostructures can be designed and fabricated for plasmonic devices at nanoscale. Fundamental properties for both surface plasmon polaritons (SPP) and localized surface plasmons (LSP) arise a new insight and understanding for the electro-optical device investigations, such as plasmonic nanofocusing, low-loss plasmon waveguide and active plasmonic detectors for energy harvesting. Here, we review some typical functional plasmonic nanostructures and nanosmart devices emerging from our individual and collaborative research works.

  11. Platinum-palladium bimetallic nanoparticles on graphitic carbon nitride modified carbon black: A highly electroactive and durable catalyst for electrooxidation of alcohols

    NASA Astrophysics Data System (ADS)

    Qian, Huayu; Chen, Shouwen; Fu, Yongsheng; Wang, Xin

    2015-12-01

    A composite catalyst consisting of Pt-Pd bimetallic nanoparticles (NPs) and graphitic carbon nitride (g-C3N4) modified carbon black (CB) is designed and fabricated by a facile two-step approach. The resulting catalyst exhibits unprecedented high catalytic activity and excellent long-term stability for electrooxidation of alcohols (methanol, ethanol, ethylene glycol and glycerol) in alkaline media. The superior electrochemical performance of the composite catalyst is attributed to the specific characteristics of the unique nanostructure and the synergistic effects of individual components, including the complementary roles of Pt (dehydrogenation site) and Pd (removal of CO-like species), the template effect of the planar amino group of g-C3N4 for the dispersed decoration of Pt-Pd NPs, the high specific surface area of CB for the rapid diffusion of electrolyte and removal of the carbonaceous intermediates, as well as the structural stability of the support based on covalent interaction between g-C3N4 and CB for maintaining the durability of the catalytic system.

  12. Noble metal-based bimetallic nanoparticles: the effect of the structure on the optical, catalytic and photocatalytic properties.

    PubMed

    Zaleska-Medynska, Adriana; Marchelek, Martyna; Diak, Magdalena; Grabowska, Ewelina

    2016-03-01

    Nanoparticles composed of two different metal elements show novel electronic, optical, catalytic or photocatalytic properties from monometallic nanoparticles. Bimetallic nanoparticles could show not only the combination of the properties related to the presence of two individual metals, but also new properties due to a synergy between two metals. The structure of bimetallic nanoparticles can be oriented in random alloy, alloy with an intermetallic compound, cluster-in-cluster or core-shell structures and is strictly dependent on the relative strengths of metal-metal bond, surface energies of bulk elements, relative atomic sizes, preparation method and conditions, etc. In this review, selected properties, such as structure, optical, catalytic and photocatalytic of noble metals-based bimetallic nanoparticles, are discussed together with preparation routes. The effects of preparation method conditions as well as metal properties on the final structure of bimetallic nanoparticles (from alloy to core-shell structure) are followed. The role of bimetallic nanoparticles in heterogeneous catalysis and photocatalysis are discussed. Furthermore, structure and optical characteristics of bimetallic nanoparticles are described in relation to the some features of monometallic NPs. Such a complex approach allows to systematize knowledge and to identify the future direction of research.

  13. Controlled Surface Segregation Leads to Efficient Coke-Resistant Nickel/Platinum Bimetallic Catalysts for the Dry Reforming of Methane

    SciTech Connect

    Li, Lidong; Zhou, Lu; Ould-Chikh, Samy; Anjum, Dalaver H.; Kanoun, Mohammed B.; Scaranto, Jessica; Hedhili, Mohamed N.; Khalid, Syed; Laveille, Paco V.; Lawrence D'Souza; Clo, Alain; Basset, Jean-Marie

    2015-02-03

    The surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. Moreover, the evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core–shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. The catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.

  14. Surface plasmon resonance sensing of a biomarker of Alzheimer disease in an intensity measurement mode with a bimetallic chip

    NASA Astrophysics Data System (ADS)

    Kim, Hyung Jin; Sohn, Young-Soo; Kim, Chang-duk; Jang, Dae-ho

    2016-09-01

    A surface plasmon resonance (SPR) sensor system with a bimetallic chip has been utilized to sense the very low concentration of amyloid-beta (A β)(1-42) by measurement of the reflectance variation. The bimetallic chip was comprised of Au (10 nm) and Ag (40 nm) on Cr (2 nm)-coated BK-7 glass substrate. Protein A was used to efficiently immobilize the antibody of A β(1-42) on the surface of the bimetallic chip. The reflectance curve of the bimetallic chip represented a narrower linewidth compared to that of the conventional gold (Au) chip. The SPR sensor using the bimetallic chip in the intensity interrogation mode acquired the response of A β(1-42) at concentrations of 250, 500, 750 and 1,000 pg/ml. The calibration plot showed a linear relationship between the mean reflectance variation and the A β(1-42) concentration. The results proved that the SPR sensor system with the bimetallic chip in the intensity interrogation mode can successfully detect various concentrations of A β(1-42), including critical concentration, to help diagnose Alzheimer's disease.

  15. Kinetics and mechanism of the liquid-phase oxidation of cyclohexene. V. Oxidation of cyclohexene in the presence of bimetallic catalysts

    SciTech Connect

    Baevskii, M.Yu.; Litvintsev, I.Yu.; Sapunov, V.N.

    1988-11-01

    The kinetics of the liquid-phase oxidation of cyclohexene in the presence of homogeneous bimetallic catalysts Co-V, Pb-V, Pb-Mo was investigated. It was shown that the activity of the bimetallic catalyst found is determined to a large degree by the nature of the epoxiding metal. A general model is proposed for the oxidation of cyclohexene in the presence of bimetallic catalysts.

  16. Expanding the plasmonic response of bimetallic nanoparticles by laser seeding

    NASA Astrophysics Data System (ADS)

    Peláez, R. J.; Rodríguez, C. E.; Afonso, C. N.

    2016-03-01

    This work explores a cost-effective route to enhance the tuning range of the optical response of metal nanostructures on substrates beyond the ranges that are achievable through the nanostructure dimensions, composition or dewetting processes. The new route (laser seeding) uses single nanosecond laser pulses to induce dewetting in regions of a metal layer deposited on a glass substrate followed by the deposition of a second metal layer, both layers being deposited by pulsed laser deposition. In order to show the possibilities of this new route, we have chosen that the two metals were different, namely Ag and Au. The comparison of the optical response of these regions to those that were laser irradiated after deposition of the second metal layer shows that while nanoalloyed nanoparticles (NPs) are formed in the latter case, the NPs produced in the former case have a heterogeneous structure. The interface between the two metals is either sharp or a narrow region where they have mixed depending on the laser fluence used. While the nanoalloyed NPs exhibit a single, narrow surface plasmon resonance (SPR), the heterogeneous NPs show broader SPRs that peak in the near infrared and depending on conditions exhibit even two clear SPRs. The laser seeding approach in the conditions used in this work allows for the expansion of the tuning range of the color to the blue-green region, i.e. beyond the region that can be achieved through nanoalloyed NPs (yellow-red region). In addition, the results presented foresee the laser seeding route as a means to produce round and almost isolated NPs in an enhanced range of diameters.

  17. Nanostructured catalyst supports

    SciTech Connect

    Zhu, Yimin; Goldman, Jay L.; Qian, Baixin; Stefan, Ionel C.

    2015-09-29

    The present invention relates to SiC nanostructures, including SiC nanopowder, SiC nanowires, and composites of SiC nanopowder and nanowires, which can be used as catalyst supports in membrane electrode assemblies and in fuel cells. The present invention also relates to composite catalyst supports comprising nanopowder and one or more inorganic nanowires for a membrane electrode assembly.

  18. Measuring Strong Nanostructures

    SciTech Connect

    Minor, Andy

    2008-01-01

    Andy Minor of Berkeley Lab's National Center for Electron Microscopy explains measuring stress and strain on nanostructures with the In Situ Microscope. More information:http://newscenter.lbl.gov/press-releases/2008/10/20/engineering-nanoparticles-for-maximum-strength/

  19. Combustion Synthesis of Nanostructures

    NASA Astrophysics Data System (ADS)

    Huczko, A.; Lange, H.; Chojecki, G.; Cudziłło, S.; Zhu, Y. Q.; Walton, D. R. M.; Kroto, H. W.; Presz, A.; Diduszko, R.

    2002-10-01

    Novel carbon and inorganic 1D nanostructures were prepared by combustion of metal-polytetrafluoroethylene (PTFE) systems in a calorimetric bomb. The high carbon yield from silicon-containing PTFE starting materials is due to the production and volatility of SiF4.

  20. Nanostructured catalyst supports

    DOEpatents

    Zhu, Yimin; Goldman, Jay L.; Qian, Baixin; Stefan, Ionel C.

    2012-10-02

    The present invention relates to SiC nanostructures, including SiC nanopowder, SiC nanowires, and composites of SiC nanopowder and nanowires, which can be used as catalyst supports in membrane electrode assemblies and in fuel cells. The present invention also relates to composite catalyst supports comprising nanopowder and one or more inorganic nanowires for a membrane electrode assembly.

  1. Aspartame-stabilized gold-silver bimetallic biocompatible nanostructures with plasmonic photothermal properties, antibacterial activity, and long-term stability.

    PubMed

    Fasciani, Chiara; Silvero, M Jazmin; Anghel, Maria Alexandra; Argüello, Gerardo A; Becerra, Maria Cecilia; Scaiano, Juan C

    2014-12-17

    Gold-silver core-shell nanoparticles stabilized with a common sweetener, aspartame (AuNP@Ag@Asm), combine the antimicrobial properties of silver with the photoinduced plasmon-mediated photothermal effects of gold. The particles were tested with several bacterial strains, while biocompatibility was verified with human dermal fibroblasts. PMID:25487127

  2. Aspartame-stabilized gold-silver bimetallic biocompatible nanostructures with plasmonic photothermal properties, antibacterial activity, and long-term stability.

    PubMed

    Fasciani, Chiara; Silvero, M Jazmin; Anghel, Maria Alexandra; Argüello, Gerardo A; Becerra, Maria Cecilia; Scaiano, Juan C

    2014-12-17

    Gold-silver core-shell nanoparticles stabilized with a common sweetener, aspartame (AuNP@Ag@Asm), combine the antimicrobial properties of silver with the photoinduced plasmon-mediated photothermal effects of gold. The particles were tested with several bacterial strains, while biocompatibility was verified with human dermal fibroblasts.

  3. Fabrication of transition metal-containing nanostructures via polymer templates for a multitude of applications

    NASA Astrophysics Data System (ADS)

    Lu, Jennifer Qing

    Nanostructures such as carbon nanotubes and semiconducting nanowires offer great technological promise due to their remarkable properties. The lack of a rational synthesis method prevents fabricating these nanostructures with desirable and consistent properties at predefined locations for device applications. In this thesis, employing polymer templates, a variety of highly ordered catalytically active transition metal nanostructures, ranging from single metallic nanoparticles of Fe, Co, Ni, Au and bimetallic nanoparticles of Ni/Fe and Co/Mo to Fe-rich silicon oxide nanodomains with uniform and tunable size and spacing have been successfully synthesized. These nanostructures have been demonstrated to be excellent catalyst systems for the synthesis of carbon nanotube and silicon nanowire. High quality, small diameter carbon nanotubes and nanowires with narrow size distribution have been successfully attained. Because these catalytically active nanostructures are uniformly distributed and do not agglomerate at the growth temperatures, uniform, high density and high quality carbon nanotube mats have been obtained. Since this polymer template approach is fully compatible with conventional top-down photolithography, lithographically selective growth of carbon nanotubes on a surface or suspended carbon nanotubes across trenches have been produced by using existing semiconductor processing. We have also shown the feasibility of producing carbon nanotubes and silicon nanowires at predefined locations on a wafer format and established a wafer-level carbon nanotube based device fabrication process. The ability of the polymer template approach to control catalyst systems at the nano-, micro- and macro-scales paves a pathway for commercialization of these 1D nanostructure-enabled devices. Beside producing well-defined, highly ordered discrete catalytically active metal-containing nanostructures by the polymer template approach, Au and Ag nanotextured surfaces have also been

  4. Uncovering the Stabilization Mechanism in Bimetallic Ruthenium-Iridium Anodes for Proton Exchange Membrane Electrolyzers.

    PubMed

    Saveleva, Viktoriia A; Wang, Li; Luo, Wen; Zafeiratos, Spyridon; Ulhaq-Bouillet, Corinne; Gago, Aldo S; Friedrich, K Andreas; Savinova, Elena R

    2016-08-18

    Proton exchange membrane (PEM) electrolyzers are attracting an increasing attention as a promising technology for the renewable electricity storage. In this work, near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is applied for in situ monitoring of the surface state of membrane electrode assemblies with RuO2 and bimetallic Ir0.7Ru0.3O2 anodes during water splitting. We demonstrate that Ir protects Ru from the formation of an unstable hydrous Ru(IV) oxide thereby rendering bimetallic Ru-Ir oxide electrodes with higher corrosion resistance. We further show that the water splitting occurs through a surface Ru(VIII) intermediate, and, contrary to common opinion, the presence of Ir does not hinder its formation. PMID:27477824

  5. Structure Evolution and Associated Catalytic Properties of Pt-Sn Bimetallic Nanoparticles.

    PubMed

    Rong, Hongpan; Niu, Zhiqiang; Zhao, Yafan; Cheng, Hao; Li, Zhi; Ma, Lei; Li, Jun; Wei, Shiqiang; Li, Yadong

    2015-08-17

    Bimetallic nanoparticles (NPs) often show new catalytic properties that are different from those of the parent metals. Carefully exploring the structures of bimetallic NPs is a prerequisite for understanding the structure-associated properties. Herein, binary PtSn NPs with tunable composition are prepared in a controllable manner. X-ray characterizations reveal that their structures evolve from SnO2-x -patched PtSn alloys to SnO2-x -patched Pt clusters when more tin is incorporated. An obvious composition-dependent catalytic performance is observed for the hydrogenation of α,β-unsaturated aldehydes: the selectivity to unsaturated alcohol increases substantially at high tin content, whereas the reaction rate follows a volcano shape. Furthermore, Pt sites are responsible for hydrogen dissociation, whereas oxygen vacancy (Ovac ) sites, provided by SnO2-x , drastically enhance the adsorption of carbonyl group.

  6. XPS/STM study of model bimetallic Pd-Au/HOPG catalysts

    NASA Astrophysics Data System (ADS)

    Bukhtiyarov, Andrey V.; Prosvirin, Igor P.; Bukhtiyarov, Valerii I.

    2016-03-01

    The preparation of model bimetallic Pd-Au/HOPG catalysts has been investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) techniques. Initially, model "core-shell" type Pd-Au/HOPG catalysts with similar particle size distribution (5-8 nm), but with different densities of particle locations on the HOPG surface and Pd/Au atomic ratios are prepared. Further, their thermal stability is studied within a temperature range of 50-500 °C at UHV conditions. It has been shown that annealing the model catalysts at a temperature range of 300-400 °C leads to formation of Pd-Au alloyed particles. Enhancement of heating temperature up to 500 °C results in sintering of bimetallic nanoparticles. Contribution of different parameters controlling the properties of Pd-Au alloyed particles has been discussed.

  7. Synthesis, characterization, and growth simulations of Cu–Pt bimetallic nanoclusters

    PubMed Central

    Khanal, Subarna; Spitale, Ana; Bhattarai, Nabraj; Bahena, Daniel; Velazquez-Salazar, J Jesus; Mejía-Rosales, Sergio

    2014-01-01

    Summary Highly monodispersed Cu–Pt bimetallic nanoclusters were synthesized by a facile synthesis approach. Analysis of transmission electron microscopy (TEM) and spherical aberration (C s)-corrected scanning transmission electron microscopy (STEM) images shows that the average diameter of the Cu–Pt nanoclusters is 3.0 ± 1.0 nm. The high angle annular dark field (HAADF-STEM) images, intensity profiles, and energy dispersive X-ray spectroscopy (EDX) line scans, allowed us to study the distribution of Cu and Pt with atomistic resolution, finding that Pt is embedded randomly in the Cu lattice. A novel simulation method is applied to study the growth mechanism, which shows the formation of alloy structures in good agreement with the experimental evidence. The findings give insight into the formation mechanism of the nanosized Cu–Pt bimetallic catalysts. PMID:25247120

  8. Remarkable enhancement of electrocatalytic activity by tuning the interface of Pd-Au bimetallic nanoparticle tubes.

    PubMed

    Cui, Chun-Hua; Yu, Jin-Wen; Li, Hui-Hui; Gao, Min-Rui; Liang, Hai-Wei; Yu, Shu-Hong

    2011-05-24

    The interface, which formed in a bimetallic system, is a critical issue to investigate the fundamental mechanism of enhanced catalytic activity. Here, we designed unsupported Pd-Au bimetallic nanoparticle tubes with a tunable interface, which was qualitatively controlled by the proportion of Pd and Au nanoparticles (NPs), to demonstrate the remarkably enhanced effect of Pd and Au NPs in electro-oxidation of ethanol. The results demonstrated that the electrocatalytic activity is highly relative to the interface and has no direct relation with individual metal component in the Pd-Au system. This effect helps us in achieving a fundamental understanding of the relationship between their activity and the interface structure and chemical properties and, consequently, is helpful in designing new catalysts with high performances. PMID:21506570

  9. Synergistic Effects in Bimetallic Palladium-Copper Catalysts Improve Selectivity in Oxygenate Coupling Reactions.

    PubMed

    Goulas, Konstantinos A; Sreekumar, Sanil; Song, Yuying; Kharidehal, Purnima; Gunbas, Gorkem; Dietrich, Paul J; Johnson, Gregory R; Wang, Y C; Grippo, Adam M; Grabow, Lars C; Gokhale, Amit A; Toste, F Dean

    2016-06-01

    Condensation reactions such as Guerbet and aldol are important since they allow for C-C bond formation and give higher molecular weight oxygenates. An initial study identified Pd-supported on hydrotalcite as an active catalyst for the transformation, although this catalyst showed extensive undesirable decarbonylation. A catalyst containing Pd and Cu in a 3:1 ratio dramatically decreased decarbonylation, while preserving the high catalytic rates seen with Pd-based catalysts. A combination of XRD, EXAFS, TEM, and CO chemisorption and TPD revealed the formation of CuPd bimetallic nanoparticles with a Cu-enriched surface. Finally, density functional theory studies suggest that the surface segregation of Cu atoms in the bimetallic alloy catalyst produces Cu sites with increased reactivity, while the Pd sites responsible for unselective decarbonylation pathways are selectively poisoned by CO. PMID:27195582

  10. Platinum-ruthenium bimetallic clusters on graphite: a comparison of vapor deposition and electroless deposition methods.

    PubMed

    Galhenage, Randima P; Xie, Kangmin; Diao, Weijian; Tengco, John Meynard M; Seuser, Grant S; Monnier, John R; Chen, Donna A

    2015-11-14

    Bimetallic Pt-Ru clusters have been grown on highly ordered pyrolytic graphite (HOPG) surfaces by vapor deposition and by electroless deposition. These studies help to bridge the material gap between well-characterized vapor deposited clusters and electrolessly deposited clusters, which are better suited for industrial catalyst preparation. In the vapor deposition experiments, bimetallic clusters were formed by the sequential deposition of Pt on Ru or Ru on Pt. Seed clusters of the first metal were grown on HOPG surfaces that were sputtered with Ar(+) to introduce defects, which act as nucleation sites for Pt or Ru. On the unmodified HOPG surface, both Pt and Ru clusters preferentially nucleated at the step edges, whereas on the sputtered surface, clusters with relatively uniform sizes and spatial distributions were formed. Low energy ion scattering experiments showed that the surface compositions of the bimetallic clusters are Pt-rich, regardless of the order of deposition, indicating that the interdiffusion of metals within the clusters is facile at room temperature. Bimetallic clusters on sputtered HOPG were prepared by the electroless deposition of Pt on Ru seed clusters from a Pt(+2) solution using dimethylamine borane as the reducing agent at pH 11 and 40 °C. After exposure to the electroless deposition bath, Pt was selectively deposited on Ru, as demonstrated by the detection of Pt on the surface by XPS, and the increase in the average cluster height without an increase in the number of clusters, indicating that Pt atoms are incorporated into the Ru seed clusters. Electroless deposition of Ru on Pt seed clusters was also achieved, but it should be noted that this deposition method is extremely sensitive to the presence of other metal ions in solution that have a higher reduction potential than the metal ion targeted for deposition.

  11. Validation of Two Hydrocodes with a Bi-Metallic Shaped Charge Experiment

    SciTech Connect

    Ingraham, Daniel J.

    2012-08-16

    Staggered grid (SGH) and cell-centered (CCH) Lagrangian Hydro are two approaches to modeling high explosives (HE) experiments. HE experiments involve complex flows. For example, the discontinuity in the tangential velocity across a frictionless contact surface. In this work, the SGH and CCH schemes with a contact surface algorithm are used to simulate a bimetallic shaped charge experiment using FLAG. Experiment will be performed at LANL in the coming year and used to validate the SGH and CCH schemes results.

  12. Nonlinear absorption tuning by composition control in bimetallic plasmonic nanoprism arrays

    NASA Astrophysics Data System (ADS)

    Cesca, Tiziana; Michieli, Niccolò; Kalinic, Boris; Sánchez-Espinoza, Ana; Rattin, Marco; Russo, Valentina; Mattarello, Valentina; Scian, Carlo; Mazzoldi, Paolo; Mattei, Giovanni

    2015-07-01

    The nonlinear absorption properties of bidimensional arrays of Au-Ag bilayered nanoprisms have been investigated by z-scan measurements as a function of the bimetallic nanoprism composition. A tunable ps laser system was used to excite the ultrafast, electronic nonlinear response matching the laser wavelength with the quadrupolar surface plasmon resonances, in the visible range, of each nanoprism array. Due to the strong electromagnetic field confinement effects at the nanoprism tips, demonstrated by finite element method simulations, these nanosystems proved to have enhanced nonlinear optical properties. Moreover, a tunable changeover from reverse saturable absorption (RSA) to saturable absorption (SA) can be obtained by properly controlling the bimetallic composition of the nanoprisms, without modifying the overall morphology of the nanosystems. This capability makes these nanosystems extremely interesting for the realization of solid-state nanophotonic devices with enhanced ultrafast nonlinear optical properties.The nonlinear absorption properties of bidimensional arrays of Au-Ag bilayered nanoprisms have been investigated by z-scan measurements as a function of the bimetallic nanoprism composition. A tunable ps laser system was used to excite the ultrafast, electronic nonlinear response matching the laser wavelength with the quadrupolar surface plasmon resonances, in the visible range, of each nanoprism array. Due to the strong electromagnetic field confinement effects at the nanoprism tips, demonstrated by finite element method simulations, these nanosystems proved to have enhanced nonlinear optical properties. Moreover, a tunable changeover from reverse saturable absorption (RSA) to saturable absorption (SA) can be obtained by properly controlling the bimetallic composition of the nanoprisms, without modifying the overall morphology of the nanosystems. This capability makes these nanosystems extremely interesting for the realization of solid

  13. Platinum-ruthenium bimetallic clusters on graphite: a comparison of vapor deposition and electroless deposition methods.

    PubMed

    Galhenage, Randima P; Xie, Kangmin; Diao, Weijian; Tengco, John Meynard M; Seuser, Grant S; Monnier, John R; Chen, Donna A

    2015-11-14

    Bimetallic Pt-Ru clusters have been grown on highly ordered pyrolytic graphite (HOPG) surfaces by vapor deposition and by electroless deposition. These studies help to bridge the material gap between well-characterized vapor deposited clusters and electrolessly deposited clusters, which are better suited for industrial catalyst preparation. In the vapor deposition experiments, bimetallic clusters were formed by the sequential deposition of Pt on Ru or Ru on Pt. Seed clusters of the first metal were grown on HOPG surfaces that were sputtered with Ar(+) to introduce defects, which act as nucleation sites for Pt or Ru. On the unmodified HOPG surface, both Pt and Ru clusters preferentially nucleated at the step edges, whereas on the sputtered surface, clusters with relatively uniform sizes and spatial distributions were formed. Low energy ion scattering experiments showed that the surface compositions of the bimetallic clusters are Pt-rich, regardless of the order of deposition, indicating that the interdiffusion of metals within the clusters is facile at room temperature. Bimetallic clusters on sputtered HOPG were prepared by the electroless deposition of Pt on Ru seed clusters from a Pt(+2) solution using dimethylamine borane as the reducing agent at pH 11 and 40 °C. After exposure to the electroless deposition bath, Pt was selectively deposited on Ru, as demonstrated by the detection of Pt on the surface by XPS, and the increase in the average cluster height without an increase in the number of clusters, indicating that Pt atoms are incorporated into the Ru seed clusters. Electroless deposition of Ru on Pt seed clusters was also achieved, but it should be noted that this deposition method is extremely sensitive to the presence of other metal ions in solution that have a higher reduction potential than the metal ion targeted for deposition. PMID:26018140

  14. Homogeneity and elemental distribution in self-assembled bimetallic Pd-Pt aerogels prepared by a spontaneous one-step gelation process.

    PubMed

    Oezaslan, M; Liu, W; Nachtegaal, M; Frenkel, A I; Rutkowski, B; Werheid, M; Herrmann, A-K; Laugier-Bonnaud, C; Yilmaz, H-C; Gaponik, N; Czyrska-Filemonowicz, A; Eychmüller, A; Schmidt, T J

    2016-07-27

    a commercially available unsupported Pt black catalyst. We show that the Pd-Pt aerogels possess a high utilization of catalytically active centers for electrocatalytic applications based on the nanostructured bimetallic framework. Knowledge about the homogeneity and chemical distribution of the bimetallic aerogels can help to further optimize their preparation by the spontaneous one-step gelation process and to tune their electrocatalytic reactivity. PMID:27411594

  15. Platinum indium bimetallic in silicalite: Preparation, characterization and use in the vinylcyclohexene transformation

    SciTech Connect

    Meriaudeau, P.; Thangaraj, A.; Naccache, C.

    1996-12-31

    The discovery of bimetallic catalysts such as Pt-Re, Pt-Ir, Pt-Sn has been a major improvement in the reforming process. The metal support was chlorinated alumina. Another generation of reforming catalysts consisted of Pt supported on non acid zeolite, KL zeolite being preferred. Recently a patent from Mobil (1) claimed for the reforming of C{sub 6}-C{sub 8} n-alkanes a catalyst constituted by platinum on an indium silicalite; these solids are able to reform n-octane into ethylbenzene (EBZ) and styrene (STY). PtIn/silicalite catalysts were reinvestigated and the high performances of this type of material attributed to the existence of small PtIn clusters as well to the shape selectivity of the silicalite (2a). Also, it has been shown that PtIn bimetallic clusters supported on NaY zeolite was active and selective in the dehydrogenation of light alkanes but these materials suffered from fast deactivation (2b). In this work, we have extended the studies of the dehydrogenation-dehydrocyclisation of alkanes over PtIn bimetallic supported on silicalite to the reaction of vinylcyclohexene (VCHx) over these materials.

  16. Ferrocenyl-cymantrenyl hetero-bimetallic chalcones: Synthesis, structure and biological properties

    NASA Astrophysics Data System (ADS)

    Mishra, Sasmita; Tirkey, Vijaylakshmi; Ghosh, Avishek; Dash, Hirak R.; Das, Surajit; Shukla, Madhulata; Saha, Satyen; Mobin, Sheikh M.; Chatterjee, Saurav

    2015-04-01

    Two new ferrocenyl-cymantrenyl bimetallic chalcones, [(CO)3Mn(η5-C5H4)C(O)CHdbnd CH(η5-C5H4)Fe(η5-C5H5)] (1) and [{(CO)3Mn(η5-C5H4)C(O)CHdbnd CH(η5-C5H4)}2Fe] (2) have been synthesized. Their reactivity study with triphenylphosphine and bis-(diphenylphosphino)ferrocene led to the isolation of phosphine substituted bimetallic chalcones (3-6). Single crystal X-ray structural characterization for 1 and its phosphine analogue (3) reveals their different conformational identity with anti-conformation for 1, while syn-conformation for 3. Investigation of antimalarial and antibacterial activities was carried out for compounds 1 and 2 against two strains of Plasmodium falciparum (3D7, K1) and four bacterial strains. TD-DFT calculation was performed for compound 1 and electrochemical properties were studied for bimetallic chalcone compounds by cyclic voltammetric technique.

  17. Monodispersed bimetallic PdAg nanoparticles with twinned structures: formation and enhancement for the methanol oxidation.

    PubMed

    Yin, Zhen; Zhang, Yining; Chen, Kai; Li, Jing; Li, Wenjing; Tang, Pei; Zhao, Huabo; Zhu, Qingjun; Bao, Xinhe; Ma, Ding

    2014-01-01

    Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd₈₀Ag₂₀, Pd₆₅Ag₃₅ and Pd₄₆Ag₅₄ can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the size-selection and relax process via the coalescence or aggregation of the primary nanoclusters. The as-prepared PdAg can be supported on the carbon black without any post-treatment, which exhibited high electro-oxidation activity towards methanol oxidation under alkaline media. More importantly, carbon-supported Pd₈₀Ag₂₀ nanoparticles reveal distinctly superior activities for the methanol oxidation, even if compared with commercial Pt/C electro-catalyst. It is concluded that the enhanced activity is dependant on the unique twinning structure with heterogeneous phase due to the dominating coalescence growth in EG ternary system. PMID:24608736

  18. Monodispersed bimetallic PdAg nanoparticles with twinned structures: Formation and enhancement for the methanol oxidation

    PubMed Central

    Yin, Zhen; Zhang, Yining; Chen, Kai; Li, Jing; Li, Wenjing; Tang, Pei; Zhao, Huabo; Zhu, Qingjun; Bao, Xinhe; Ma, Ding

    2014-01-01

    Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd80Ag20, Pd65Ag35 and Pd46Ag54 can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the size-selection and relax process via the coalescence or aggregation of the primary nanoclusters. The as-prepared PdAg can be supported on the carbon black without any post-treatment, which exhibited high electro-oxidation activity towards methanol oxidation under alkaline media. More importantly, carbon-supported Pd80Ag20 nanoparticles reveal distinctly superior activities for the methanol oxidation, even if compared with commercial Pt/C electro-catalyst. It is concluded that the enhanced activity is dependant on the unique twinning structure with heterogeneous phase due to the dominating coalescence growth in EG ternary system. PMID:24608736

  19. Bimetallic non-alloyed NPs for improving the broadband optical absorption of thin amorphous silicon substrates

    PubMed Central

    2014-01-01

    We propose the use of bimetallic non-alloyed nanoparticles (BNNPs) to improve the broadband optical absorption of thin amorphous silicon substrates. Isolated bimetallic NPs with uniform size distribution on glass and silicon are obtained by depositing a 10-nm Au film and annealing it at 600°C; this is followed by an 8-nm Ag film annealed at 400°C. We experimentally demonstrate that the deposition of gold (Au)-silver (Ag) bimetallic non-alloyed NPs (BNNPs) on a thin amorphous silicon (a-Si) film increases the film's average absorption and forward scattering over a broad spectrum, thus significantly reducing its total reflection performance. Experimental results show that Au-Ag BNNPs fabricated on a glass substrate exhibit resonant peaks at 437 and 540 nm and a 14-fold increase in average forward scattering over the wavelength range of 300 to 1,100 nm in comparison with bare glass. When deposited on a 100-nm-thin a-Si film, Au-Ag BNNPs increase the average absorption and forward scattering by 19.6% and 95.9% compared to those values for Au NPs on thin a-Si and plain a-Si without MNPs, respectively, over the 300- to 1,100-nm range. PMID:24725390

  20. Electrodeposition of Au/Ag bimetallic dendrites assisted by Faradaic AC-electroosmosis flow

    SciTech Connect

    Ji, Jianlong; Li, Pengwei; Sang, Shengbo Zhang, Wendong Li, Gang; Hu, Jie; Zhou, Zhaoying Yang, Xing; Dong, Hualai

    2014-03-15

    Au/Ag bimetallic dendrites were synthesized successfully from the corresponding aqueous solution via the AC electrodeposition method. Both of the morphologies and compositions could be tuned by the electrolyte concentration and AC frequency. The prepared bimetallic dendrites were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and UV–vis spectroscopy. The underlying dendrite growth mechanism was then proposed in the context of the Directed Electrochemical Nanowires Assembly (DENA) models. Owing to the unscreened voltage dropping in the electrolyte bulk, electromigration dominates the species flux process, and cations tend to accumulate in areas with strong electric field intensity, such as electrode edges. Moreover, Faradaic AC-electro-osmosis (ACEO) flow could increase the effective diffusion layer thickness in these areas during the electrochemical reaction, and leads to dendrite growth. Further Micro-Raman observations illustrated that the Au/Ag bimetallic dendrites exhibited pronounced surface-enhanced Raman scattering (SERS) activity, using 4-mercaptopyridine (4-MP) as model molecules.

  1. Experimental and computational investigations of sulfur-resistant bimetallic catalysts for reforming of biomass gasification products

    SciTech Connect

    Rangan, Meghana; Yung, Matthew M.; Medlin, J. William

    2011-11-17

    A combination of density functional theory (DFT) calculations and experimental studies of supported catalysts was used to identify H{sub 2}S-resistant biomass gasification product reforming catalysts. DFT calculations were used to search for bimetallic, nickel-based (1 1 1) surfaces with lower sulfur adsorption energies and enhanced ethylene adsorption energies. These metrics were used as predictors for H{sub 2}S resistance and activity toward steam reforming of ethylene, respectively. Relative to Ni, DFT studies found that the Ni/Sn surface alloy exhibited enhanced sulfur resistance and the Ni/Ru system exhibited an improved ethylene binding energy with a small increase in sulfur binding energy. A series of supported bimetallic nickel catalysts was prepared and screened under model ethylene reforming conditions and simulated biomass tar reforming conditions. The observed experimental trends in activity were consistent with theoretical predictions, with observed reforming activities in the order Ni/Ru > Ni > Ni/Sn. Interestingly, Ni/Ru showed a high level of resistance to sulfur poisoning compared with Ni. This sulfur resistance can be partly explained by trends in sulfur versus ethylene binding energy at different types of sites across the bimetallic surface.

  2. Efficient method for the conversion of agricultural waste into sugar alcohols over supported bimetallic catalysts.

    PubMed

    Tathod, Anup P; Dhepe, Paresh L

    2015-02-01

    Promoter effect of Sn in the PtSn/γ-Al2O3 (AL) and PtSn/C bimetallic catalysts is studied for the conversion of variety of substrates such as, C5 sugars (xylose, arabinose), C6 sugars (glucose, fructose, galactose), hemicelluloses (xylan, arabinogalactan), inulin and agricultural wastes (bagasse, rice husk, wheat straw) into sugar alcohols (sorbitol, mannitol, xylitol, arabitol, galactitol). In all the reactions, PtSn/AL showed enhanced yields of sugar alcohols by 1.5-3 times than Pt/AL. Compared to C, AL supported bimetallic catalysts showed prominent enhancement in the yields of sugar alcohols. Bimetallic catalysts characterized by X-ray diffraction study revealed the stability of catalyst and absence of alloy formation thereby indicating that Pt and Sn are present as individual particles in PtSn/AL. The TEM analysis also confirmed stability of the catalysts and XPS study disclosed formation of electron deficient Sn species which helps in polarizing carbonyl bond to achieve enhanced hydrogenation activity. PMID:25453932

  3. Characterization of Bimetallic Castings with an Austenitic Working Surface Layer and an Unalloyed Cast Steel Base

    NASA Astrophysics Data System (ADS)

    Wróbel, Tomasz

    2014-05-01

    The paper presents the technology of bimetallic castings based on the founding method of layer coating directly in the cast process of the so-called method of mold cavity preparation. The prepared castings consist of two fundamental parts, i.e., the base and the working surface layer. The base part of the bimetallic casting is typical foundry material, i.e., unalloyed cast steel, whereas the working layer is a plate of austenitic alloy steel sort X2CrNi 18-9. The quality of the joint between the base part and the working layer was evaluated on the basis of ultrasonic non-destructive testing and structure examinations containing metallographic macro- and microscopic studies with the use of a light microscope (LOM) with microhardness measurements and a scanning electron microscope (SEM) with microanalysis of the chemical composition (energy dispersive spectroscopy—EDS). On the basis of the obtained results it was confirmed that the decisive phenomena needed to create a permanent joint between the two components of the bimetallic casting are carbon and heat transport in the direction from the high-carbon and hot base material which was poured into the mold in the form of liquid metal to the low-carbon and cold material of the working layer which was placed in the mold cavity in the form of a monolithic insert.

  4. Electrodeposition of Au/Ag bimetallic dendrites assisted by Faradaic AC-electroosmosis flow

    NASA Astrophysics Data System (ADS)

    Ji, Jianlong; Li, Pengwei; Sang, Shengbo; Zhang, Wendong; Zhou, Zhaoying; Yang, Xing; Dong, Hualai; Li, Gang; Hu, Jie

    2014-03-01

    Au/Ag bimetallic dendrites were synthesized successfully from the corresponding aqueous solution via the AC electrodeposition method. Both of the morphologies and compositions could be tuned by the electrolyte concentration and AC frequency. The prepared bimetallic dendrites were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and UV-vis spectroscopy. The underlying dendrite growth mechanism was then proposed in the context of the Directed Electrochemical Nanowires Assembly (DENA) models. Owing to the unscreened voltage dropping in the electrolyte bulk, electromigration dominates the species flux process, and cations tend to accumulate in areas with strong electric field intensity, such as electrode edges. Moreover, Faradaic AC-electro-osmosis (ACEO) flow could increase the effective diffusion layer thickness in these areas during the electrochemical reaction, and leads to dendrite growth. Further Micro-Raman observations illustrated that the Au/Ag bimetallic dendrites exhibited pronounced surface-enhanced Raman scattering (SERS) activity, using 4-mercaptopyridine (4-MP) as model molecules.

  5. Laser synthesis of ligand-free bimetallic nanoparticles for plasmonic applications.

    PubMed

    Intartaglia, R; Das, G; Bagga, K; Gopalakrishnan, A; Genovese, A; Povia, M; Di Fabrizio, E; Cingolani, R; Diaspro, A; Brandi, F

    2013-03-01

    A picosecond laser ablation approach has been developed for the synthesis of ligand-free AuAg bimetallic NPs where the relative amount of Ag is controlled in situ through a laser shielding effect. Various measurements, such as optical spectroscopy, transmission electron microscopy combined with energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometry, revealed the generation of homogenous 15 nm average size bimetallic NPs with different compositions and tunable localized surface plasmon resonance. Furthermore, ligand-free metallic nanoparticles with respect to chemically synthesized nanoparticles display outstanding properties, i.e. featureless Raman background spectrum, which is a basic requirement in many plasmonic applications such as Surface Enhanced Raman Spectroscopy. Various molecules were chemisorbed on the nanoparticle and SERS investigations were carried out, by varying the laser wavelength. The SERS enhancement factor for AuAg bimetallic NPs shows an enhancement factor of about 5.7 × 10(5) with respect to the flat AuAg surface. PMID:23196320

  6. Chemisorption and FTIR study of bimetallic Pt-Au/SiO sub 2 catalysts

    SciTech Connect

    Balakrishnan, K.; Sachdev, A.; Schwank, J. )

    1990-02-01

    Pt/SiO{sub 2}, Au/SiO{sub 2}, and bimetallic Pt-Au/SiO{sub 2} catalysts were prepared by incipient wetness impregnation of nonporous SiO{sub 2}. The catalysts were characterized after reduction in H{sub 2} by static volumetric chemisorption and infrared spectroscopy. For the monometallic and the bimetallic catalysts, H{sub 2}, O{sub 2} and CO were used as adsorbates at room temperature. Additionally, for the monometallic Au/SiO{sub 2} catalyst, O{sub 2} adsorption at 473 K was also used. Infrared spectra of adsorbed CO were obtained on all catalysts. Addition of gold decreased the uptake of all three adsorbates at room temperature, without significantly influencing the relative amounts of weakly held adsorbed species which could be removed upon pumping for 30 min. Agreeing with CO chemisorption data, the total integrated intensity of the linear CO band decreased with increasing Au content. The IR results indicated a predominantly geometric effect of Au causing a shift of the linear CO band to lower wavenumbers. The shift could be rationalized in terms of decreased dipole-dipole coupling of adsorbed CO species. The results are discussed within the context of a previous investigation using electron microscopy, TPR, and reactivity data. Portions of the bimetallic catalysts were subjected to three high-temperature oxidation/reduction cycles and characterized by static chemisorption of H{sub 2} to investigate the effect of this thermal treatment on Pt dispersion.

  7. Growth and characterization of CNT Forests using Bimetallic Nanoparticles as Catalyst

    NASA Astrophysics Data System (ADS)

    Lee, Kyung-Hwan; Sra, A.; Jang, H.; Choi, B.; Overzet, L.; Lee, G.; Yang, D.

    2008-10-01

    We study the growth of Multiwall carbon nanotubes (MWCNT) using bimetallic nanoparticles (NP) as catalyst rather than zerovalent metal ions such as Fe, Ni, Co. One advantage of using bimetallic NP is that both the size and shape and composition (atomic ordering) can be controlled. We will describe a simple method of producing bimetallic Fe-Pt, Fe-Co alloy nanoparticles and compare MWCNT growth using them to Fe catalyst growth. The synthesis of Fe, Fe-Pt, Fe-Co NP was carried out using a bottom-up polyol process. Subsequent growth of MWCNT forests was accomplished by PECVD using acetylene as precursor. TEM and SEM analysis of the sample cross-section grown at substrate temperature of 680 ^oC indicates that the diameters of the CNTs are ˜ 10-20 nm while height of the forest varies from 30 μm for Fe to 5 μm for Fe-Pt and 80-100 μm for Fe-Co. The number of walls in the CNTs and the graphitization content could be manipulated by varying the temperature (increasing to 760 ^oC) or by pre-treatment of the nanoparticles with oxygen plasma.

  8. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Final report

    SciTech Connect

    Chunshan Song; Schobert, H.H.; Parfitt, D.P.

    1997-11-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that dispersed catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on exploring novel bimetallic dispersed catalysts for coal liquefaction and the effectiveness of temperature-programmed liquefaction using dispersed catalysts. The primary objective of this research was to explore novel bimetallic dispersed catalysts from organometallic molecular precursors, that could be used in low concentrations but exhibit relatively high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. We have synthesized and tested various catalyst precursors in liquefaction of subbituminous and bituminous coals and in model compound studies to examine how do the composition and structure of the catalytic precursors affect their effectiveness for coal liquefaction under different reaction conditions, and how do these factors affect their catalytic functions for hydrogenation of polyaromatic hydrocarbons, for cleavage of C-C bonds in polycyclic systems such as 4-(1-naphthylmethyl)bibenzyl, for hydrogenolysis of C-O bond such as that in dinaphthylether, for hydrodeoxygenation of phenolic compounds and other oxygen-containing compounds such as xanthene, and for hydrodesulfurization of polycyclic sulfur compounds such as dibenzothiophene. The novel bimetallic and monometallic precursors synthesized and tested in this project include various Mo- and Fe-based compounds.

  9. Laser synthesis of ligand-free bimetallic nanoparticles for plasmonic applications.

    PubMed

    Intartaglia, R; Das, G; Bagga, K; Gopalakrishnan, A; Genovese, A; Povia, M; Di Fabrizio, E; Cingolani, R; Diaspro, A; Brandi, F

    2013-03-01

    A picosecond laser ablation approach has been developed for the synthesis of ligand-free AuAg bimetallic NPs where the relative amount of Ag is controlled in situ through a laser shielding effect. Various measurements, such as optical spectroscopy, transmission electron microscopy combined with energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometry, revealed the generation of homogenous 15 nm average size bimetallic NPs with different compositions and tunable localized surface plasmon resonance. Furthermore, ligand-free metallic nanoparticles with respect to chemically synthesized nanoparticles display outstanding properties, i.e. featureless Raman background spectrum, which is a basic requirement in many plasmonic applications such as Surface Enhanced Raman Spectroscopy. Various molecules were chemisorbed on the nanoparticle and SERS investigations were carried out, by varying the laser wavelength. The SERS enhancement factor for AuAg bimetallic NPs shows an enhancement factor of about 5.7 × 10(5) with respect to the flat AuAg surface.

  10. Manganese Nanostructures and Magnetism

    NASA Astrophysics Data System (ADS)

    Simov, Kirie Rangelov

    The primary goal of this study is to incorporate adatoms with large magnetic moment, such as Mn, into two technologically significant group IV semiconductor (SC) matrices, e.g. Si and Ge. For the first time in the world, we experimentally demonstrate Mn doping by embedding nanostructured thin layers, i.e. delta-doping. The growth is observed by in-situ scanning tunneling microscopy (STM), which combines topographic and electronic information in a single image. We investigate the initial stages of Mn monolayer growth on a Si(100)(2x1) surface reconstruction, develop methods for classification of nanostructure types for a range of surface defect concentrations (1.0 to 18.2%), and subsequently encapsulate the thin Mn layer in a SC matrix. These experiments are instrumental in generating a surface processing diagram for self-assembly of monoatomic Mn-wires. The role of surface vacancies has also been studied by kinetic Monte Carlo modeling and the experimental observations are compared with the simulation results, leading to the conclusion that Si(100)(2x1) vacancies serve as nucleation centers in the Mn-Si system. Oxide formation, which happens readily in air, is detrimental to ferromagnetism and lessens the magnetic properties of the nanostructures. Therefore, the protective SC cap, composed of either Si or Ge, serves a dual purpose: it is both the embedding matrix for the Mn nanostructured thin film and a protective agent for oxidation. STM observations of partially deposited caps ensure that the nanostructures remain intact during growth. Lastly, the relationship between magnetism and nanostructure types is established by an in-depth study using x-ray magnetic circular dichroism (XMCD). This sensitive method detects signals even at coverages less than one atomic layer of Mn. XMCD is capable of discerning which chemical compounds contribute to the magnetic moment of the system, and provides a ratio between the orbital and spin contributions. Depending on the amount

  11. Antibacterial Au nanostructured surfaces

    NASA Astrophysics Data System (ADS)

    Wu, Songmei; Zuber, Flavia; Brugger, Juergen; Maniura-Weber, Katharina; Ren, Qun

    2016-01-01

    We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all the Au nanostructures, regardless their shapes, exhibited similar excellent antibacterial properties. A comparison of live cells attached to nanotopographic surfaces showed that the number of live S. aureus cells was <1% of that from flat and rough reference surfaces. Our micro/nanofabrication process is a scalable approach based on cost-efficient self-organization and provides potential for further developing functional surfaces to study the behavior of microbes on nanoscale topographies.We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It

  12. Nanostructured Superhydrophobic Coatings

    SciTech Connect

    2009-03-01

    This factsheet describes a research project that deals with the nanostructured superhydrophobic (SH) powders developed at ORNL. This project seeks to (1) improve powder quality; (2) identify binders for plastics, fiberglass, metal (steel being the first priority), wood, and other products such as rubber and shingles; (3) test the coated product for coating quality and durability under operating conditions; and (4) application testing and production of powders in quantity.

  13. Pickled luminescent silicon nanostructures

    NASA Astrophysics Data System (ADS)

    Boukherroub, R.; Morin, S.; Wayner, D. D. M.; Lockwood, D. J.

    2001-05-01

    In freshly prepared porous Si, the newly exposed silicon-nanostructure surface is protected with a monolayer of hydrogen, which is very reactive and oxidizes in air leading to a loss of luminescence intensity and a degradation of the electronic properties. We report a surface passivation approach based on organic modification that stabilizes the luminescence. This novel 'pickling' process not only augments the desired optoelectronic properties, but also is adaptable to further chemical modification for integration into chemical and biophysical sensors.

  14. Bimetallic Nanocatalysts in Mesoporous Silica for Hydrogen Production from Coal-Derived Fuels

    SciTech Connect

    Kuila, Debasish; Ilias, Shamsuddin

    2013-02-13

    In steam reforming reactions (SRRs) of alkanes and alcohols to produce H2, noble metals such as platinum (Pt) and palladium (Pd) are extensively used as catalyst. These metals are expensive; so, to reduce noble-metal loading, bi-metallic nanocatalysts containing non-noble metals in MCM-41 (Mobil Composition of Material No. 41, a mesoporous material) as a support material with high-surface area were synthesized using one-pot hydrothermal procedure with a surfactant such as cetyltrimethylammonium bromide (CTAB) as a template. Bi-metallic nanocatalysts of Pd-Ni and Pd-Co with varying metal loadings in MCM-41 were characterized by x-ray diffraction (XRD), N2 adsorption, and Transmission electron microscopy (TEM) techniques. The BET surface area of MCM-41 (~1000 m2/g) containing metal nanoparticles decreases with the increase in metal loading. The FTIR studies confirm strong interaction between Si-O-M (M = Pd, Ni, Co) units and successful inclusion of metal into the mesoporous silica matrix. The catalyst activities were examined in steam reforming of methanol (SRM) reactions to produce hydrogen. Reference tests using catalysts containing individual metals (Pd, Ni and Co) were also performed to investigate the effect of the bimetallic system on the catalytic behavior in the SRM reactions. The bimetallic system remarkably improves the hydrogen selectivity, methanol conversion and stability of the catalyst. The results are consistent with a synergistic behavior for the Pd-Ni-bimetallic system. The performance, durability and thermal stability of the Pd-Ni/MCM-41 and Pd-Co/MCM-41 suggest that these materials may be promising catalysts for hydrogen production from biofuels. A part of this work for synthesis and characterization of Pd-Ni-MCM-41 and its activity for SRM reactions has been published (“Development of Mesoporous Silica Encapsulated Pd-Ni Nanocatalyst for Hydrogen Production” in “Production and Purification of Ultraclean

  15. Alternative nanostructures for thermophones.

    PubMed

    Aliev, Ali E; Mayo, Nathanael K; Jung de Andrade, Monica; Robles, Raquel O; Fang, Shaoli; Baughman, Ray H; Zhang, Mei; Chen, Yongsheng; Lee, Jae Ah; Kim, Seon Jeong

    2015-05-26

    Thermophones are highly promising for applications such as high-power SONAR arrays, flexible loudspeakers, and noise cancellation devices. So far, freestanding carbon nanotube aerogel sheets provide the most attractive performance as a thermoacoustic heat source. However, the limited accessibility of large-size freestanding carbon nanotube aerogel sheets and other even more exotic materials recently investigated hampers the field. We describe alternative materials for a thermoacoustic heat source with high-energy conversion efficiency, additional functionalities, environmentally friendly, and cost-effective production technologies. We discuss the thermoacoustic performance of alternative nanostructured materials and compare their spectral and power dependencies of sound pressure in air. We demonstrate that the heat capacity of aerogel-like nanostructures can be extracted by a thorough analysis of the sound pressure spectra. The study presented here focuses on engineering thermal gradients in the vicinity of nanostructures and subsequent heat dissipation processes from the interior of encapsulated thermoacoustic projectors. Applications of thermoacoustic projectors for high-power SONAR arrays, sound cancellation, and optimal thermal design, regarding enhanced energy conversion efficiency, are discussed.

  16. Coherent control near metallic nanostructures

    SciTech Connect

    Efimov, Ilya; Efimov, Anatoly

    2008-01-01

    We study coherent control in the vicinity of metallic nanostructures. Unlike in the case of control in gas or liquid phase, the collective response of electrons in a metallic nanostructure can significantly enhance different frequency components of the control field. This enhancement strongly depends on the geometry of the nanostructure and can substantially modify the temporal profile of the local control field. The changes in the amplitude and phase of the control field near the nanostructure are studied using linear response theory. The inverse problem of finding the external electromagnetic field to generate the desired local control field is considered and solved.

  17. Selective Hydrogenation of Phenylacetylene on Bimetallic Cu-Pd and Cu-Pt Catalysts

    NASA Astrophysics Data System (ADS)

    Cladaras, George

    The development of selective catalysts has become a key concept in improving the efficiency of processes. Controlling the product distribution of a reaction can result in fewer by-products and reduce energy requirements for process equipment downstream. The selective hydrogenation of alkynes to alkenes is of major importance to industrial polymerization processes where alkyne/diene impurities can poison the polymerization catalyst and have an unwanted inhibiting effect on the growth of the polymer chain. In many circumstances, bimetallic catalysts have proved to have superior catalytic properties such as greater activity, selectivity or stability compared to their monometallic analogs. A study by the Sykes group (Chemistry, Tufts) in collaboration with our group has shown that in ultra-high vacuum (UHV), the addition of Pd minority species (0.01 ML) onto an otherwise inert Cu(111) single crystal surface can activate the Cu surface for selective hydrogenation reactions. This thesis work is an extension of the surface science study to the preparation of bimetallic catalysts at the nanoscale and their testing in hydrogenation reactions at ambient reaction conditions. The overall aim of this work was to develop single atom alloy Pd-Cu and Pt-Cu catalysts which are highly active and selective for the selective hydrogenation reaction of phenylacetylene to styrene. The bimetallic catalysts were prepared by a colloidal synthesis of Cu nanoparticles immobilized on gamma-alumina support and the precious metals as a minority species were deposited by galvanic replacement. The prepared materials and synthesis technique were characterized with electron microscopy (TEM), UV-Vis spectroscopy, X-Ray diffraction (XRD), temperature programmed reduction (TPR), BET surface area measurements, chemisorption experiments and X-ray photoelectron spectroscopy (XPS). The resulting catalysts can be described as gamma-Al2O3 supported Cu nanoparticles with a narrow size distribution. The Pt

  18. PREFACE: Nanostructured surfaces

    NASA Astrophysics Data System (ADS)

    Palmer, Richard E.

    2003-10-01

    We can define nanostructured surfaces as well-defined surfaces which contain lateral features of size 1-100 nm. This length range lies well below the micron regime but equally above the Ångstrom regime, which corresponds to the interatomic distances on single-crystal surfaces. This special issue of Journal of Physics: Condensed Matter presents a collection of twelve papers which together address the fabrication, characterization, properties and applications of such nanostructured surfaces. Taken together they represent, in effect, a status report on the rapid progress taking place in this burgeoning area. The first four papers in this special issue have been contributed by members of the European Research Training Network ‘NanoCluster’, which is concerned with the deposition, growth and characterization of nanometre-scale clusters on solid surfaces—prototypical examples of nanoscale surface features. The paper by Vandamme is concerned with the fundamentals of the cluster-surface interaction; the papers by Gonzalo and Moisala address, respectively, the optical and catalytic properties of deposited clusters; and the paper by van Tendeloo reports the application of transmission electron microscopy (TEM) to elucidate the surface structure of spherical particles in a catalyst support. The fifth paper, by Mendes, is also the fruit of a European Research Training Network (‘Micro-Nano’) and is jointly contributed by three research groups; it reviews the creation of nanostructured surface architectures from chemically-synthesized nanoparticles. The next five papers in this special issue are all concerned with the characterization of nanostructured surfaces with scanning tunnelling microscopy (STM) and atomic force microscopy (AFM). The papers by Bolotov, Hamilton and Dunstan demonstrate that the STM can be employed for local electrical measurements as well as imaging, as illustrated by the examples of deposited clusters, model semiconductor structures and real

  19. Reverse Micelle Synthesis and Characterization of Supported Pt/Ni Bimetallic Catalysts on gamma-Al2O3

    SciTech Connect

    B Cheney; J Lauterbach; J Chen

    2011-12-31

    Reverse micelle synthesis was used to improve the nanoparticle size uniformity of bimetallic Pt/Ni nanoparticles supported on {gamma}-Al{sub 2}O{sub 3}. Two impregnation methods were investigated to optimize the use of the micelle method: (1) step-impregnation, where Ni nanoparticles were chemically reduced in microemulsion and then supported, followed by Pt deposition using incipient wetness impregnation, and (2) co-impregnation, where Ni and Pt were chemically reduced simultaneously in microemulsion and then supported. Transmission electron microscopy (TEM) was used to characterize the particle size distribution. Atomic absorption spectroscopy (AAS) was used to perform elemental analysis of bimetallic catalysts. Extended X-ray absorption fine structure (EXAFS) measurements were utilized to confirm the formation of the Pt-Ni bimetallic bond in the step-impregnated catalyst. CO pulse chemisorption and Fourier transform infrared spectroscopy (FTIR) studies of 1,3-butadiene hydrogenation in a batch reactor were performed to determine the catalytic activity. Step-impregnated Pt/Ni catalyst demonstrated enhanced hydrogenation activity over the parent monometallic Pt and Ni catalysts due to bimetallic bond formation. The catalyst synthesized using co-impregnation showed no enhanced activity, behaving similarly to monometallic Ni. Overall, our results indicate that reverse micelle synthesis combined with incipient wetness impregnation produced small, uniform nanoparticles with bimetallic bonds that enhanced hydrogenation activity.

  20. Rapid, general synthesis of PdPt bimetallic alloy nanosponges and their enhanced catalytic performance for ethanol/methanol electrooxidation in an alkaline medium.

    PubMed

    Zhu, Chengzhou; Guo, Shaojun; Dong, Shaojun

    2013-01-14

    We have demonstrated a rapid and general strategy to synthesize novel three-dimensional PdPt bimetallic alloy nanosponges in the absence of a capping agent. Significantly, the as-prepared PdPt bimetallic alloy nanosponges exhibited greatly enhanced activity and stability towards ethanol/methanol electrooxidation in an alkaline medium, which demonstrates the potential of applying these PdPt bimetallic alloy nanosponges as effective electrocatalysts for direct alcohol fuel cells. In addition, this simple method has also been applied for the synthesis of AuPt, AuPd bimetallic, and AuPtPd trimetallic alloy nanosponges. The as-synthesized three-dimensional bimetallic/trimetallic alloy nanosponges, because of their convenient preparation, well-defined sponge-like network, large-scale production, and high electrocatalytic performance for ethanol/methanol electrooxidation, may find promising potential applications in various fields, such as formic acid oxidation or oxygen reduction reactions, electrochemical sensors, and hydrogen-gas sensors.

  1. Infrared study of CO adsorption on magnesia-supported ruthenium, gold, and bimetallic ruthenium-gold clusters

    SciTech Connect

    Schwank, J.; Parravano, G.; Gruber, H.L.

    1980-01-01

    An infrared study of CO adsorption on magnesia-supported ruthenium, gold, and bimetallic ruthenium-gold clusters provided evidence for metal-support interaction in the single-metal catalysts and for metal-metal interaction in the bimetallic catalysts which indicated that all the metal present existed as bimetallic clusters and that gold did not form separate clusters or segregate at the surface. The IR study was made at various degrees of coverage with CO of catalysts containing 2.1-4.7% metal (0, 11, 36, 90, and 100Vertical Bar3< gold) on magnesia and pretreated in hydrogen, helium or oxygen, and a comparison sample of 5% ruthenium on silica.

  2. Nanostructures for peroxidases

    PubMed Central

    Carmona-Ribeiro, Ana M.; Prieto, Tatiana; Nantes, Iseli L.

    2015-01-01

    Peroxidases are enzymes catalyzing redox reactions that cleave peroxides. Their active redox centers have heme, cysteine thiols, selenium, manganese, and other chemical moieties. Peroxidases and their mimetic systems have several technological and biomedical applications such as environment protection, energy production, bioremediation, sensors and immunoassays design, and drug delivery devices. The combination of peroxidases or systems with peroxidase-like activity with nanostructures such as nanoparticles, nanotubes, thin films, liposomes, micelles, nanoflowers, nanorods and others is often an efficient strategy to improve catalytic activity, targeting, and reusability. PMID:26389124

  3. Biomimetics of photonic nanostructures

    NASA Astrophysics Data System (ADS)

    Parker, Andrew R.; Townley, Helen E.

    2007-06-01

    Biomimetics is the extraction of good design from nature. One approach to optical biomimetics focuses on the use of conventional engineering methods to make direct analogues of the reflectors and anti-reflectors found in nature. However, recent collaborations between biologists, physicists, engineers, chemists and materials scientists have ventured beyond experiments that merely mimic what happens in nature, leading to a thriving new area of research involving biomimetics through cell culture. In this new approach, the nanoengineering efficiency of living cells is harnessed and natural organisms such as diatoms and viruses are used to make nanostructures that could have commercial applications.

  4. Nanoindentation of Carbon Nanostructures.

    PubMed

    Kumar, Dinesh; Singh, Karamjit; Verma, Veena; Bhatti, H S

    2016-06-01

    In the present research paper carbon nanostructures viz. single walled carbon nanotubes, multi-walled carbon nanotubes, single walled carbon nanohorns and graphene nanoplatelets have been synthesized by CVD technique, hydrothermal method, DC arc discharge method in liquid nitrogen and microwave technique respectively. After synthesis 5 mm thick pallets of given nanomaterial are prepared by making a paste in isopropyl alcohol and using polyvinylidene difluoride as a binder and then these pallets were used for nanoindentation measurements. Hardness, reduced modulus, stiffness, contact height and contact area have been measured using nanoindenter. PMID:27427726

  5. Controlled synthesis and synergistic effects of graphene-supported PdAu bimetallic nanoparticles with tunable catalytic properties

    NASA Astrophysics Data System (ADS)

    Liu, Chang-Hai; Liu, Rui-Hua; Sun, Qi-Jun; Chang, Jian-Bing; Gao, Xu; Liu, Yang; Lee, Shuit-Tong; Kang, Zhen-Hui; Wang, Sui-Dong

    2015-03-01

    Graphene-supported bimetallic nanoparticles are promising nanocatalysts, which can show strong and tunable catalytic activity and selectivity. Herein room-temperature-ionic-liquid-assisted metal sputtering is utilized to synthesize PdAu bimetallic nanoparticles on graphene with bare surface, small size, high surface density and controlled Pd-to-Au ratio. This controllable synthetic approach is green-chemistry compatible and totally free of additives and byproducts. The supported PdAu nanoparticles show excellent catalytic capabilities for both oxidation and reduction reactions, strongly dependent on the Pd-to-Au ratio. A strong correlation among catalytic performance, bimetallic composition and charge redistribution in the PdAu nanoparticles has been demonstrated. The results suggest that sufficient Au d-holes appear to be significant to the catalysis of oxidation reaction, and a metallic Pd surface is critical to the catalysis of reduction reaction. By the present method, the bimetallic combination can be tailored for distinct types of catalytic reactions.Graphene-supported bimetallic nanoparticles are promising nanocatalysts, which can show strong and tunable catalytic activity and selectivity. Herein room-temperature-ionic-liquid-assisted metal sputtering is utilized to synthesize PdAu bimetallic nanoparticles on graphene with bare surface, small size, high surface density and controlled Pd-to-Au ratio. This controllable synthetic approach is green-chemistry compatible and totally free of additives and byproducts. The supported PdAu nanoparticles show excellent catalytic capabilities for both oxidation and reduction reactions, strongly dependent on the Pd-to-Au ratio. A strong correlation among catalytic performance, bimetallic composition and charge redistribution in the PdAu nanoparticles has been demonstrated. The results suggest that sufficient Au d-holes appear to be significant to the catalysis of oxidation reaction, and a metallic Pd surface is critical

  6. The synergistic effect in the Fe-Co bimetallic catalyst system for the growth of carbon nanotube forests

    SciTech Connect

    Hardeman, D.; Esconjauregui, S. Cartwright, R.; D'Arsié, L.; Robertson, J.; Bhardwaj, S.; Cepek, C.; Oakes, D.; Clark, J.; Ducati, C.

    2015-01-28

    We report the growth of multi-walled carbon nanotube forests employing an active-active bimetallic Fe-Co catalyst. Using this catalyst system, we observe a synergistic effect by which—in comparison to pure Fe or Co—the height of the forests increases significantly. The homogeneity in the as-grown nanotubes is also improved. By both energy dispersive spectroscopy and in-situ x-ray photoelectron spectroscopy, we show that the catalyst particles consist of Fe and Co, and this dramatically increases the growth rate of the tubes. Bimetallic catalysts are thus potentially useful for synthesising nanotube forests more efficiently.

  7. Characterization of bimetallic Pt-Sn/Al{sub 2}O{sub 3} catalysts: Relationship between particle size and structure

    SciTech Connect

    Merlen, E.; Zanier, N.

    1996-03-01

    Pt-Sn/Al{sub 2}O{sub 3} bimetallic catalysts have been prepared using organometallic precursors and characterized. Two models depending on average platinum particle size are proposed in order to describe these solids. The catalyst obtained from a highly dispersed monometallic precursor may be described as Pt/SnO{sub x}/Al{sub 2}O{sub 3} with platinum probably in interaction with tin oxide. When the monometallic precursor has low dispersion, the bimetallic system may be described as PtSn{sup 0} + SnO{sub x}/Al{sub 2}O{sub 3}. 35 refs., 8 figs., 9 tabs.

  8. Microstructural characterization of bimetallic Ni-Pt catalysts supported on SiO 2

    NASA Astrophysics Data System (ADS)

    Arenas-Alatorre, J.; Avalos-Borja, M.; Díaz, G.

    2002-04-01

    A set of Pt, Ni and a bimetallic Ni50Pt50 catalysts supported on SiO2 of low and high surface area (S=50 and 200 m2/g) with a total metal loading of 2 wt.% was characterized by high-resolution electron microscopy (HREM), conventional transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and computational techniques such as digital processing and image simulation. Special attention was placed to the identification of intermetallic phases in the Ni50Pt50/SiO2 sample. Catalysts were prepared by impregnation and submitted to calcination-reduction activation treatments. For all the set, the increase in support's surface area led to an improvement of the metal dispersion. TEM and HREM images showed significant differences in the shape and crystalline lattice of the Pt and Ni particles in the monometallic samples taken as reference. While in Pt/SiO2 catalyst we identified only reduced Pt particles, in Ni/SiO2 some NiO particles were detected. HREM characterization of the Ni50Pt50 catalysts showed that many particles have defects such as twinning and dislocations. Cubo-octahedral shapes were predominant in the bimetallic catalyst. Crystal lattice and angles measurements were consistent with the identification of NiPt and/or Ni3Pt intermetallic phases. Superlattice structures were also identified and confirmed by image simulation. EDS analysis on a particle by particle basis confirmed that in bimetallic catalysts supported in SiO2 of low and high surface area, particles were present consisting of Ni-rich, nominal and Pt-rich metal compositions. Pt-only particles were found but no Ni-only particles were detected. Among the possibilities, NiPt and Ni3Pt compositions were identified.

  9. Novel supported bimetallic carbide catalysts for coprocessing of coal with waste materials

    SciTech Connect

    S.T. Oyama; D.F. Cox; C. Song; F. Allen

    1999-12-15

    In this reporting period the authors have continued their investigation of bimetallic nitride and carbide compounds for use in coprocessing of coal and waste plastics or rubber. Following up on their finding of a class of bimetallic nitrides, reported in the last period, they now report on a new family of bimetallic oxycarbides M{sup I}-M{sup II}-O-C (M{sup I} = Mo, W; M{sup II} = V, Nb, Cr, Fe, Co, Ni). They have carried out a preliminary test of the compounds with a model coal liquid feed and find that, in general, these carbides are even more active than the nitrides. They have identified Nb-Mo-O-C as the most promising catalyst, and this catalyst together with Mo{sub 2}C, the most active single-metal carbide are being investigated for the coprocessing reaction. Comparison is made to standard sulfide catalysts. The latter reaction is carried out in batch autoclave systems, so that preliminary tests are first carried out with a simpler five-component feedstock. The feedstock is a multi-component model mixture that simulates the combined feed of coal and waste materials. The idea is to use different compounds that are specific for each reaction type but have no overlapping products. The proposed design involves a 5-component mixture containing: 4-(1-naphthylmethyl)bibenzyl, abbreviated as NMBB, pyrene, tetradecane, dibenzothiophene and quinoline. NMBB simulates the aromatic-aliphatic as well as aliphatic-aliphatic C-C bonds in coal and in some aromatic plastics such as polystyrene. This compound has been used as a probe molecule in previous studies. Pyrene represents polyaromatic structures in coal, while tetradecane is representative of polyethylene-type plastics in chemical reactivity. Dibenzothiophene and quinoline provide sulfur and nitrogen content.

  10. Surface plasmon polariton assisted optical switching in noble bimetallic nanoparticle system

    SciTech Connect

    Dhara, Sandip E-mail: chenkh@pub.iams.sinica.edu.tw; Lu, C.-Y.; Tu, W.-S.; Magudapathy, P.; Huang, Y.-F.; Chen, K.-H. E-mail: chenkh@pub.iams.sinica.edu.tw

    2015-01-12

    Photoresponse of bimetallic Au-Ag nanoparticle embedded soda glass (Au-Ag@SG) substrate is reported for surface plasmon assisted optical switching using 808 nm excitation. Au-Ag@SG system is made by an ion beam technique where Ag{sup +} is introduced first in the soda glass matrix by ion exchange technique. Subsequently, 400 keV Au{sup +} is implanted in the sample for different fluences, which is followed by an ion beam annealing process using 1 MeV Si{sup +} at a fixed fluence of 2 × 10{sup 16} ions·cm{sup −2}. Characteristic surface plasmon resonance (SPR) peaks around 400 and 550 nm provided evidence for the presence of Au and Ag nanoparticles. An optical switching in the Au-Ag@SG system with 808 nm, which is away from the characteristic SPR peaks of Ag and Au nanoparticles, suggests the possible role of two photon absorption (TPA) owing to the presence of interacting electric dipole in these systems. The role of surface plasmon polariton is emphasized for the propagation of electronic carrier belonging to the conduction electron of Au-Ag system in understanding the observed photoresponse. Unique excitation dependent photoresponse measurements confirm the possible role of TPA process. A competitive interband and intraband transitions in the bimetallic system of Au and Ag, which may be primarily responsible for the observation, are validated qualitatively using finite difference time domain calculations where inter-particle separation of Au and Ag plays an important role. Thus, a smart way of optical switching can be envisaged in noble bimetallic nanocluster system where long wavelength with higher skin depth can be used for communication purpose.

  11. The role of nanostructures and hydrophilicity in osseointegration: In-vitro protein-adsorption and blood-interaction studies.

    PubMed

    Kopf, Brigitte S; Ruch, Sylvie; Berner, Simon; Spencer, Nicholas D; Maniura-Weber, Katharina

    2015-08-01

    Protein adsorption and blood coagulation play important roles in the early stages of osseointegration and are strongly influenced by surface properties. We present a systematic investigation of the influence of different surface properties on the adsorption of the blood proteins fibrinogen and fibronectin and the degree of early blood coagulation. Experiments on custom-made and commercially available, microroughened hydrophobic titanium (Ti) surfaces (Ti SLA-Hphob ), hydrophilic (Hphil ) microroughened Ti surfaces with nanostructures (Ti SLActive-Hphil NS), and on bimetallic Ti zirconium alloy (TiZr, Roxolid®) samples were performed, to study the biological response in relation to the surface wettability and the presence of nanostructures (NS). Protein adsorption on the different substrates showed a highly significant effect of surface NS. Hydrophilicity alone did not significantly enhance protein adsorption. Overall, the combination of NS and hydrophilicity led to the highest adsorption levels; independent of whether Ti or TiZr were used. Hydrophilicity induced a strong effect on blood coagulation, whereas the effect of NS alone was weak. The combination of both surface characteristics led to early and most pronounced blood-coagulation. Therefore, nanostructured, hydrophilic Ti and TiZr surfaces may perform better in terms of osseointegration due to continuous protein adsorption and the formation of a layer of blood components on the implant surface.

  12. Unraveling Surface Plasmon Decay in Core-Shell Nanostructures toward Broadband Light-Driven Catalytic Organic Synthesis.

    PubMed

    Huang, Hao; Zhang, Lei; Lv, Zhiheng; Long, Ran; Zhang, Chao; Lin, Yue; Wei, Kecheng; Wang, Chengming; Chen, Lu; Li, Zhi-Yuan; Zhang, Qun; Luo, Yi; Xiong, Yujie

    2016-06-01

    Harnessing surface plasmon of metal nanostructures to promote catalytic organic synthesis holds great promise in solar-to-chemical energy conversion. High conversion efficiency relies not only on broadening the absorption spectrum but on coupling the harvested energy into chemical reactions. Such coupling undergoes hot-electron transfer and photothermal conversion during the decay of surface plasmon; however, the two plasmonic effects are unfortunately entangled, making their individual roles still under debate. Here, we report that in a model system of bimetallic Au-Pd core-shell nanostructures the two effects can be disentangled through tailoring the shell thickness at atomic-level precision. As demonstrated by our ultrafast absorption spectroscopy characterizations, the achieved tunability of the two effects in a model reaction of Pd-catalyzed organic hydrogenation offers a knob for enhancing energy coupling. In addition, the two intrinsic plasmonic modes at 400-700 and 700-1000 nm in the bar-shaped nanostructures allow for utilizing photons to a large extent in full solar spectrum. This work establishes a paradigmatic guidance toward designing plasmonic-catalytic nanomaterials for enhanced solar-to-chemical energy conversion.

  13. Magnetic Properties of Nanostructures

    NASA Astrophysics Data System (ADS)

    Ciraldo, John

    2007-10-01

    The recent development of the superlattice nanowire pattern transfer (SNAP) technique has enabled the fabrication of complex molecular-electronic circuits at unprecedented densities. In this project, we explore the possibility of extending this technique to generate comparably dense arrays of nanoscale giant magnetoresistive (GMR) and tunneling magnetoresistive (TMR) devices. My primary contribution to this project has focused on using a vibrating sample magnetometer (VSM), as well as a superconducting interference device (SQUID) magnetometer to monitor the magnetic properties of the devices as they are processed from thin 2D films into nanostructure arrays. This investigation allows us to investigate both fundamental and technological aspects of the nanopatterning process. For example, the effects of changing surface to volume ratios on the ferromagnetic exchange interaction and the role of various patterning techniques in determining surface chemistry and oxidation of the final nanostructures, respectively. Additionally I have worked on simulations of the materials using NIST's OOMF program, allowing me to compare actual results with theoretical expectations. I am also designing a magneto-optical Kerr effect (MOKE) detector, which will allow faster approximations of magnetic behavior.

  14. P–C-Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine–Boranes**

    PubMed Central

    Johnson, Heather C; Weller, Andrew S

    2015-01-01

    {Rh(xantphos)}-based phosphido dimers form by P–C activation of xantphos (4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) in the presence of amine–boranes. These dimers are active dehydrocoupling catalysts, forming polymeric [H2BNMeH]n from H3B⋅NMeH2 and dimeric [H2BNMe2]2 from H3B⋅NMe2H at low catalyst loadings (0.1 mol %). Mechanistic investigations support a dimeric active species, suggesting that bimetallic catalysis may be possible in amine–borane dehydropolymerization. PMID:26140498

  15. An ultrastable bimetallic carbide as platinum electrocatalyst support for highly active oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Yan, Zaoxue; Zhang, Mingmei; Xie, Jimin; Shen, Pei Kang

    2015-11-01

    Stable bimetallic carbide (Fe2MoC) with graphitized carbon (GC) as matrix has been synthesized through an ion-exchange method. The Pt nanoparticles are loaded on the GC-Fe2MoC composite to form Pt/GC-Fe2MoC electrocatalyst which shows much higher activity and stability than those of commercial Pt/C for oxygen reduction reaction in acidic media. The excellent performances of Pt/GC-Fe2MoC are mainly due to the inherent stability of GC-Fe2MoC and the promotion effect between Fe2MoC and Pt.

  16. Electrical performances of pyroelectric bimetallic strip heat engines describing a Stirling cycle

    NASA Astrophysics Data System (ADS)

    Arnaud, A.; Boughaleb, J.; Monfray, S.; Boeuf, F.; Cugat, O.; Skotnicki, T.

    2015-12-01

    This paper deals with the analytical modeling of pyroelectric bimetallic strip heat engines. These devices are designed to exploit the snap-through of a thermo-mechanically bistable membrane to transform a part of the heat flowing through the membrane into mechanical energy and to convert it into electric energy by means of a piezoelectric layer deposited on the surface of the bistable membrane. In this paper, we describe the properties of these heat engines in the case when they complete a Stirling cycle, and we evaluate the performances (available energy, Carnot efficiency...) of these harvesters at the macro- and micro-scale.

  17. Enhanced antibacterial activity of bimetallic gold-silver core-shell nanoparticles at low silver concentration

    NASA Astrophysics Data System (ADS)

    Banerjee, Madhuchanda; Sharma, Shilpa; Chattopadhyay, Arun; Ghosh, Siddhartha Sankar

    2011-12-01

    Herein we report the development of bimetallic Au@Ag core-shell nanoparticles (NPs) where gold nanoparticles (Au NPs) served as the seeds for continuous deposition of silver atoms on its surface. The core-shell structure and morphology were examined by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD). The core-shell NPs showed antibacterial activity against both Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Enterococcus faecalis and Pediococcus acidilactici) bacteria at low concentration of silver present in the shell, with more efficacy against Gram negative bacteria. TEM and flow cytometric studies showed that the core-shell NPs attached to the bacterial surface and caused membrane damage leading to cell death. The enhanced antibacterial properties of Au@Ag core-shell NPs was possibly due to the more active silver atoms in the shell surrounding gold core due to high surface free energy of the surface Ag atoms owing to shell thinness in the bimetallic NP structure.Herein we report the development of bimetallic Au@Ag core-shell nanoparticles (NPs) where gold nanoparticles (Au NPs) served as the seeds for continuous deposition of silver atoms on its surface. The core-shell structure and morphology were examined by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD). The core-shell NPs showed antibacterial activity against both Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Enterococcus faecalis and Pediococcus acidilactici) bacteria at low concentration of silver present in the shell, with more efficacy against Gram negative bacteria. TEM and flow cytometric studies showed that the core-shell NPs attached to the bacterial surface and caused membrane damage leading to cell death. The enhanced antibacterial properties of Au@Ag core-shell NPs was

  18. Free-Standing Bimetallic Nanorings and Nanoring Arrays Made by On-Wire Lithography

    SciTech Connect

    Liusman, Cipto; Li, Shuzhou; Chen, Xiaodong; Wei, Wei; Zhang, Hua; Schatz, George C.; Boey, Freddy; Mirkin, Chad A.

    2010-12-28

    This paper describes a new strategy for synthesizing free-standing bimetallic nanorings and nanoring arrays based upon on-wire lithography and a galvanic replacement reaction. The strategy allows one to tune the diameter, length, and therefore aspect ratio of the nanorings. In addition, it can be used to produce arrays of nanorings in high yield with control over number and spacing. Spectroscopic studies and discrete dipole approximation calculations show that nanoring dimers exhibit greater surface enhanced Raman scattering than the analogous nanodisk dimers.

  19. Bimetallic PtxCoy nanoparticles with curved faces for highly efficient hydrogenation of cinnamaldehyde

    NASA Astrophysics Data System (ADS)

    Gu, Yan; Zhao, Yonghui; Wu, Panpan; Yang, Bo; Yang, Nating; Zhu, Yan

    2016-05-01

    The control of the curved structure of bimetallic nanocrystals is a challenge, due to the rate differential for atom deposition and surface diffusion of alien atomic species on specific crystallographic planes of seeds. Herein, we report how to tune the degree of concavity of bimetallic PtxCoy concave nanoparticles using carboxylic acids as surfactants with an oleylamine system, leading to the specific crystallographic planes being exposed. The terminal carboxylic acids with a bridge ring or a benzene ring serving as structure regulators could direct the formation of curved faces with exposed high-index facets, and long-chain saturated fatty acids favored the production of curved faces with exposed low-index facets, while long-chain olefin acids alone benefited the formation of a flat surface with exposed low-index planes. Furthermore, these PtxCoy particles with curved faces displayed superior catalytic behaviour to cinnamaldehyde hydrogenation when compared with PtxCoy with flat faces. PtxCoy nanoparticles with curved faces exhibited over 6-fold increase in catalytic activity compared to PtxNiy nanoparticles with curved faces, and near 40-fold activity increase was observed in comparison with PtxFey nanoparticles with curved faces.The control of the curved structure of bimetallic nanocrystals is a challenge, due to the rate differential for atom deposition and surface diffusion of alien atomic species on specific crystallographic planes of seeds. Herein, we report how to tune the degree of concavity of bimetallic PtxCoy concave nanoparticles using carboxylic acids as surfactants with an oleylamine system, leading to the specific crystallographic planes being exposed. The terminal carboxylic acids with a bridge ring or a benzene ring serving as structure regulators could direct the formation of curved faces with exposed high-index facets, and long-chain saturated fatty acids favored the production of curved faces with exposed low-index facets, while long

  20. Formation of nanostructured porous Cu-Au surfaces: the influence of cationic sites on (electro)-catalysis

    NASA Astrophysics Data System (ADS)

    Najdovski, Ilija; Selvakannan, Pr.; Bhargava, Suresh K.; O'Mullane, Anthony P.

    2012-09-01

    The fabrication of nanostructured bimetallic materials through electrochemical routes offers the ability to control the composition and shape of the final material that can then be effectively applied as (electro)-catalysts. In this work a clean and transitory hydrogen bubble templating method is employed to generate porous Cu-Au materials with a highly anisotropic nanostructured interior. Significantly, the co-electrodeposition of copper and gold promotes the formation of a mixed bimetallic oxide surface which does not occur at the individually electrodeposited materials. Interestingly, the surface is dominated by Au(i) oxide species incorporated within a Cu2O matrix which is extremely effective for the industrially important (electro)-catalytic reduction of 4-nitrophenol. It is proposed that an aurophilic type of interaction takes place between both oxidized gold and copper species which stabilizes the surface against further oxidation and facilitates the binding of 4-nitrophenol to the surface and increases the rate of reaction. An added benefit is that very low gold loadings are required typically less than 2 wt% for a significant enhancement in performance to be observed. Therefore the ability to create a partially oxidized Cu-Au surface through a facile electrochemical route that uses a clean template consisting of only hydrogen bubbles should be of benefit for many more important reactions.The fabrication of nanostructured bimetallic materials through electrochemical routes offers the ability to control the composition and shape of the final material that can then be effectively applied as (electro)-catalysts. In this work a clean and transitory hydrogen bubble templating method is employed to generate porous Cu-Au materials with a highly anisotropic nanostructured interior. Significantly, the co-electrodeposition of copper and gold promotes the formation of a mixed bimetallic oxide surface which does not occur at the individually electrodeposited materials

  1. Correlating Extent of Pt–Ni Bond Formation with Low-temperature Hydrogenation of Benzene and 1,3-butadiene over Supported Pt/Ni Bimetallic Catalysts

    SciTech Connect

    Lonergan, W.; Vlachos, D; Chen, J

    2010-01-01

    Low-temperature hydrogenation of benzene and 1,3-butadiene on supported Pt/Ni catalysts have been used as probe reactions to correlate hydrogenation activity with the extent of Pt-Ni bimetallic bond formation. Pt/Ni bimetallic and Pt and Ni monometallic catalysts were supported on {gamma}-Al{sub 2}O{sub 3} using incipient wetness impregnation. Two sets of bimetallic catalysts were synthesized: one set to study the effect of metal atomic ratio and the other to study the effect of impregnation sequence. Fourier transform infrared spectroscopy (FTIR) CO adsorption studies were performed to characterize the surface composition of the bimetallic nanoparticles, and transmission electron microscopy (TEM) was utilized to characterize the particle size distribution. Batch reactor studies with FTIR demonstrated that all bimetallic catalysts outperformed monometallic catalysts for both benzene and 1,3-butadiene hydrogenation. Within the two sets of bimetallic catalysts, it was found that catalysts with a smaller Pt:Ni ratio possessed higher hydrogenation activity and that catalysts synthesized using co-impregnation had greater activity than sequentially impregnated catalysts. Extended X-ray absorption fine structure (EXAFS) measurements were performed in order to verify the extent of Pt-Ni bimetallic bond formation, which was found to correlate with the hydrogenation activity.

  2. Stoichiometrically controlled production of bimetallic Gold-Silver alloy colloids using micro-alga cultures.

    PubMed

    Dahoumane, Si Amar; Wijesekera, Kushlani; Filipe, Carlos D M; Brennan, John D

    2014-02-15

    This paper reports the production of well-defined, highly stable Ag-Au alloy nanoparticles (NPs) using living cells of Chlamydomonas reinhardtii, with the composition of the bimetallic alloys being solely determined by the stoichiometric ratio in which the metal salts were added to the cultures. The NPs exhibited a single, well-defined surface plasmon resonance (SPR) band confirming that they were made of a homogeneous population of bimetallic alloys. Particle creation by the cells occurred in three stages: (1) internalization of the noble metals by the cells and their reduction resulting in the formation of the NPs; (2) entrapment of the NPs in the extracellular matrix (ECM) surrounding the cells, where they are colloidally stabilized; and (3) release of the NPs from the ECM to the culture medium. We also investigated the effect of the addition of the metals salts on cell viability and the impact on characteristics of the NPs formed. When silver was added to the cultures, cell viability was decreased and this resulted in a ~30nm red shift on the SPR band due to changes in the surrounding environment into which the NPs were released. The same observations (in SPR and cell viability) was made when gold was added to a final concentration of 2 × 10(-4)M, but not when the concentration was equal to 10(-4)M, where cell viability was high and the red shift was negligible. PMID:24370403

  3. Synthesis and electrocatalytic activity of Au/Pt bimetallic nanodendrites for ethanol oxidation in alkaline medium.

    PubMed

    Han, Xinyi; Wang, Dawei; Liu, Dong; Huang, Jianshe; You, Tianyan

    2012-02-01

    Gold/Platinum (Au/Pt) bimetallic nanodendrites were successfully synthesized through seeded growth method using preformed Au nanodendrites as seeds and ascorbic acid as reductant. Cyclic voltammograms (CVs) of a series of Au/Pt nanodendrites modified electrodes in 1M KOH solution containing 1M ethanol showed that the electrocatalyst with a molar ratio (Au:Pt) of 3 exhibited the highest peak current density and the lowest onset potential. The peak current density of ethanol electro-oxidation on the Au(3)Pt(1) nanodendrites modified glassy carbon electrode (Au(3)Pt(1) electrode) is about 16, 12.5, and 4.5 times higher than those on the polycrystalline Pt electrode, polycrystalline Au electrode, and Au nanodendrites modified glassy carbon electrode (Au dendrites electrode), respectively. The oxidation peak potential of ethanol electro-oxidation on the Au(3)Pt(1) electrode is about 299 and 276 mV lower than those on the polycrystalline Au electrode and Au dendrites electrode, respectively. These results demonstrated that the Au/Pt bimetallic nanodendrites may find potential application in alkaline direct ethanol fuel cells (ADEFCs).

  4. Bimetallic PtxCoy nanoparticles with curved faces for highly efficient hydrogenation of cinnamaldehyde.

    PubMed

    Gu, Yan; Zhao, Yonghui; Wu, Panpan; Yang, Bo; Yang, Nating; Zhu, Yan

    2016-06-01

    The control of the curved structure of bimetallic nanocrystals is a challenge, due to the rate differential for atom deposition and surface diffusion of alien atomic species on specific crystallographic planes of seeds. Herein, we report how to tune the degree of concavity of bimetallic PtxCoy concave nanoparticles using carboxylic acids as surfactants with an oleylamine system, leading to the specific crystallographic planes being exposed. The terminal carboxylic acids with a bridge ring or a benzene ring serving as structure regulators could direct the formation of curved faces with exposed high-index facets, and long-chain saturated fatty acids favored the production of curved faces with exposed low-index facets, while long-chain olefin acids alone benefited the formation of a flat surface with exposed low-index planes. Furthermore, these PtxCoy particles with curved faces displayed superior catalytic behaviour to cinnamaldehyde hydrogenation when compared with PtxCoy with flat faces. PtxCoy nanoparticles with curved faces exhibited over 6-fold increase in catalytic activity compared to PtxNiy nanoparticles with curved faces, and near 40-fold activity increase was observed in comparison with PtxFey nanoparticles with curved faces.

  5. Stoichiometrically controlled production of bimetallic Gold-Silver alloy colloids using micro-alga cultures.

    PubMed

    Dahoumane, Si Amar; Wijesekera, Kushlani; Filipe, Carlos D M; Brennan, John D

    2014-02-15

    This paper reports the production of well-defined, highly stable Ag-Au alloy nanoparticles (NPs) using living cells of Chlamydomonas reinhardtii, with the composition of the bimetallic alloys being solely determined by the stoichiometric ratio in which the metal salts were added to the cultures. The NPs exhibited a single, well-defined surface plasmon resonance (SPR) band confirming that they were made of a homogeneous population of bimetallic alloys. Particle creation by the cells occurred in three stages: (1) internalization of the noble metals by the cells and their reduction resulting in the formation of the NPs; (2) entrapment of the NPs in the extracellular matrix (ECM) surrounding the cells, where they are colloidally stabilized; and (3) release of the NPs from the ECM to the culture medium. We also investigated the effect of the addition of the metals salts on cell viability and the impact on characteristics of the NPs formed. When silver was added to the cultures, cell viability was decreased and this resulted in a ~30nm red shift on the SPR band due to changes in the surrounding environment into which the NPs were released. The same observations (in SPR and cell viability) was made when gold was added to a final concentration of 2 × 10(-4)M, but not when the concentration was equal to 10(-4)M, where cell viability was high and the red shift was negligible.

  6. Ellagic Acid Directed Growth of Au-Pt Bimetallic Nanoparticles and Their Catalytic Applications

    NASA Astrophysics Data System (ADS)

    Barnaby, Stacey N.; Sarker, Nazmul H.; Banerjee, Ipsita A.

    2013-02-01

    In this work, we report the facile formation of bimetallic nanoparticles of Au-Pt in the presence of the plant polyphenol ellagic acid (EA). It was found that EA formed micro-fibrillar assemblies, which aggregated into micro-bundles under aqueous conditions. Those micro-bundles acted as templates for the growth of Au nanoparticles, as well as bimetallic Au-Pt nanoparticles biomimetically. At higher concentrations of EA, it was observed that in addition to forming fibrous micro-bundles, columnar assemblies of EA were formed in the presence of the metal nanoparticles. The formation of the assemblies was found to be concentration dependent. It appears that upon binding to metal ions and subsequent formation of the nanoparticles, morphological changes occur in the case of EA assemblies. The morphological changes observed were probed by electron microscopy. Further, the ability of the materials to degrade the toxic aromatic nitro compound 2-methoxy-4-nitroaniline was explored, where 50% degradation was observed within 15 min, indicating that such hybrid materials may have potential applications in environmental remediation.

  7. Characterization of Magnetic NiFe Nanoparticles with Controlled Bimetallic Composition

    SciTech Connect

    Liu, Yan; Chi, Yanxiu; Shan, Shiyao; Yin, Jun; Luo, Jin; Zhong, Chuan-Jian

    2014-02-25

    The exploration of the magnetic properties of bimetallic alloy nanoparticles for various technological applications requires the ability to control the morphology, composition, and surface properties. In this report, we describe new findings of an investigation of the morphology and composition of NiFe alloy nanoparticles synthesized under controlled conditions. The controllability over the bimetallic composition has been demonstrated by the observation of an approximate linear relationship between the composition in the nanoparticles and in the synthetic feeding. The morphology of the NiFe nanoparticles is consistent with an fcc-type alloy, with the lattice strain increasing linearly with the iron content in the nanoparticles. The alloy nanoparticles exhibit remarkable resistance to air oxidation in comparison with Ni or Fe particles. The thermal stability and the magnetic properties of the as-synthesized alloy nanoparticles are shown to depend on the composition. The alloy nanoparticles have also be sown to display low saturation magnetization and coercivity values in comparison with the Ni nanoparticles, in line with the superparamagnetic characteristic. These findings have important implications for the design of stable and controllable magnetic nanoparticles for various technological applications.

  8. Using supported Au nanoparticles as starting material for preparing uniform Au/Pd bimetallic catalysts

    SciTech Connect

    Villa, Alberto; Prati, Laura; Su, Dangshen; Wang, Di; Veith, Gabriel M

    2010-01-01

    One of the best methods for producing bulk homogeneous (composition) supported bimetallic AuPd clusters involves the immobilization of a protected Au seed followed by the addition of Pd. This paper investigates the importance of this gold seed in controlling the resulting bimetallic AuPd clusters structures, sizes and catalytic activities by investigating three different gold seeds. Uniform Au-Pd alloy were obtained when a steric/electrostatic protecting group, poly(vinyl alcohol) (PVA), was used to form the gold clusters on activated carbon (AC). In contrast Au/AC precursors prepared using Au nanoparticles with only electrostatic stabilization (tetrakis(hydroxypropyl)phosphonium chloride (THPC)), or no stabilization (magnetron sputtering) produced inhomogeneous alloys and segregation of the gold and palladium. The uniform alloyed catalyst (Pd{at}Au{sub PVA}/AC) is the most active and selective catalyst, while the inhomogenous catalysts are less active and selective. Further study of the PVA protected Au clusters revealed that the amount of PVA used is also critical for the preparation of uniform alloyed catalyst, their stability, and their catalytic activity.

  9. Fundamental studies of hydrogen chemisorption on supported monometallic and bimetallic catalysts using microcalorimetry

    SciTech Connect

    Narayan, R.L.

    1997-06-24

    Highly dispersed transition metal catalysts are used in numerous commercial processes such as hydrocarbon conversions. For example, the use of Pt supported on acidic alumina or silica-alumina for reforming of naphtha in the production of gasoline is well known. Another use of supported catalysts is in automobile emission control where supported Pt-Rh bimetallic catalysts are used. Supported Ru can be used in Fischer-Tropsch synthesis for the production of higher hydrocarbons from synthesis gas. While many of these catalyst systems have been in commercial operation for several decades there is still a lack of consensus regarding the exact role of the catalyst on a molecular level. In particular, little is known about the mechanisms operating on the catalyst surface at the high pressure and high temperature conditions typically used in commercial operations. This report contains the general introduction and conclusions and an appendix containing the operating instructions for a microcalorimeter. Three chapters have been processed separately. They are: the effect of K on the kinetics and thermodynamics of hydrogen adsorption on Ru/SiO{sub 2}; hydrogen adsorption states on silica supported Ru-Ag and Ru-Cu bimetallic catalysts investigated via microcalorimetry; a comparative study of hydrogen chemisorption on silica supported Ru, Rh, and Pt.

  10. Modification of TiO2 by Bimetallic Au-Cu Nanoparticles for Wastewater Treatment

    PubMed Central

    Hai, Zibin; Kolli, Nadia EL; Uribe, Daniel Bahena; Beaunier, Patricia; José-Yacaman, Miguel; Vigneron, Jackie; Etcheberry, Arnaud; Sorgues, Sébastien; Colbeau-Justin, Christophe; Chen, Jiafu; Remita, Hynd

    2016-01-01

    Au, Cu and bimetallic Au-Cu nanoparticles were synthesized on the surface of commercial TiO2 compounds (P25) by reduction of the metal precursors with tetrakis (hydroxymethyl) phosphonium chloride (THPC) (0.5 % in weight). The alloyed structure of Au-Cu NPs was confirmed by HAADF-STEM, EDS, HRTEM and XPS techniques. The photocatalytic properties of the modified TiO2 have been studied for phenol photodegradation in aqueous suspensions under UV-visible irradiation. The modification by the metal nanoparticles induces an increase in the photocatalytic activity. The highest photocatalytic activity is obtained with Au-Cu/TiO2 (Au/Cu 1:3). Their electronic properties have been studied by time resolved microwave conductivity (TRMC) to follow the charge-carrier dynamics. TRMC measurements show that the TiO2 modification with Au, Cu and Au-Cu nanoparticles plays a role in charge-carrier separations increasing the activity under UV-light. Indeed, the metal nanoparticles act as a sink for electron, decreasing the charge carrier recombination. The TRMC measurements show also that the bimetallic Au-Cu nanoparticles are more efficient in electron scavenging than the monometallic Au and Cu ones. PMID:27274844

  11. Bimetallic PtSn/C catalysts obtained via SOMC/M for glycerol steam reforming.

    PubMed

    Pastor-Pérez, Laura; Merlo, Andrea; Buitrago-Sierra, Robison; Casella, Mónica; Sepúlveda-Escribano, Antonio

    2015-12-01

    A detailed study on the preparation of bimetallic PtSn/C catalysts using surface-controlled synthesis methods, and on their catalytic performance in the glycerol steam reforming reaction has been carried out. In order to obtain these well-defined bimetallic phases, techniques derived from Surface Organometallic Chemistry on Metals (SOMC/M) were used. The preparation process involved the reaction between an organometallic compound ((C4H9)4Sn) and a supported transition metal (Pt) in a H2 atmosphere. Catalysts with Sn/Pt atomic ratios of 0.2, 0.3, 0.5, and 0.7 were obtained, and characterized using several techniques: ICP, H2 chemisorption, TEM and XPS. These systems were tested in the glycerol steam reforming varying the reaction conditions (glycerol concentration and reaction temperature). The best performance was observed for the catalysts with the lowest tin contents (PtSn0.2/C and PtSn0.3/C). It was observed that the presence of tin increased the catalysts' stability when working under more severe reaction conditions.

  12. Bimetallic PtSn/C catalysts obtained via SOMC/M for glycerol steam reforming.

    PubMed

    Pastor-Pérez, Laura; Merlo, Andrea; Buitrago-Sierra, Robison; Casella, Mónica; Sepúlveda-Escribano, Antonio

    2015-12-01

    A detailed study on the preparation of bimetallic PtSn/C catalysts using surface-controlled synthesis methods, and on their catalytic performance in the glycerol steam reforming reaction has been carried out. In order to obtain these well-defined bimetallic phases, techniques derived from Surface Organometallic Chemistry on Metals (SOMC/M) were used. The preparation process involved the reaction between an organometallic compound ((C4H9)4Sn) and a supported transition metal (Pt) in a H2 atmosphere. Catalysts with Sn/Pt atomic ratios of 0.2, 0.3, 0.5, and 0.7 were obtained, and characterized using several techniques: ICP, H2 chemisorption, TEM and XPS. These systems were tested in the glycerol steam reforming varying the reaction conditions (glycerol concentration and reaction temperature). The best performance was observed for the catalysts with the lowest tin contents (PtSn0.2/C and PtSn0.3/C). It was observed that the presence of tin increased the catalysts' stability when working under more severe reaction conditions. PMID:26283100

  13. Application of bimetallic iron (BioCAT slurry) for pentachlorophenol removal from sandy soil.

    PubMed

    Dien, Nguyen Thanh; De Windt, Wim; Buekens, Alfons; Chang, Moo Been

    2013-05-15

    Bimetallic iron nanoparticles have mostly been applied to the degradation of chlorinated compounds in the aqueous phase. In this study, the degradation of pentachlorophenol (PCP) spiked into sandy soil is considered as a first exploratory step for remediating PCP in real contaminated soil using a commercial preparation of bimetallic iron (Trade name BioCAT). After 21 days of treatment a PCP removal efficiency of 90% was achieved, along with 70% dechlorination efficiency, for a dosage of 600 mg BioCAT slurry/kg soil. Degradation of PCP by BioCAT follows first order kinetics in PCP. Stepwise dechlorination is the main pathway of PCP elimination from soil slurries contacted with BioCAT. Such dechlorination is confirmed by the appearance of intermediate products, as well as by release of chlorides. Additionally, the increasing pH value and the rapid decrease of the oxidation/reduction potential (ORP) also attest to the reductive dechlorination of PCP. The reaction products comprehend lower chlorinated phenols, including three TeCP isomers, four TrCP isomers, four DCP isomers, two MCP isomers and phenol. These findings indicate that BioCAT could be applied for field treatment of PCP-contaminated soil under ambient conditions.

  14. Bimetallic oxamato complexes synthesized into mesoporous matrix as precursor to tunable nanosized oxide

    SciTech Connect

    Kalinke, Lucas H.G.; Stumpf, Humberto O.; Mazali, Italo O.; Cangussu, Danielle

    2015-10-15

    Highlights: • The bimetallic oxamato complexes as single-source precursor. • We prepared into a porous silica glass tunable nanosized oxide powders. • X-ray diffraction shows the formation of CeO{sub 2}/CuO and spinel cobaltite. • The different number of IDC allows control of the nanoparticle size. - Abstract: The bimetallic complexes were employed to prepare into a porous silica glass tunable nanosized oxide powders through the single source precursor (SSP) method. These materials were prepared by first anchoring of [Cu(opba)]{sup 2−} [opba = ortho-phenylenebis(oxamato)], second by reaction in situ with second metal [Co(II) or Ce(III)] and followed by a thermal treatment. The different number of impregnation–decomposition cycles (IDC) allows control of the nanoparticle size. X-ray diffraction shows the formation of mixture CeO{sub 2}–CuO and spinel copper cobaltite. Raman spectroscopy confirmed the formation of such phases. Transmission electron microscopy images revealed that spinel cobaltite particles (8 IDC) present a mean size of about 9 nm, whereas for the CeO{sub 2}–CuO phase the particle diameters are 4 nm (2 IDC) and 8 nm (6 IDC). For CeO{sub 2}–CuO the diffuse reflectance spectroscopy indicates a consistent red shift in band gap from 3.41 to 2.87 eV with increasing of particle size due to quantum confinement effect.

  15. Particle swarm optimization of the stable structure of tetrahexahedral Pt-based bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Tun-Dong; Fan, Tian-E.; Shao, Gui-Fang; Zheng, Ji-Wen; Wen, Yu-Hua

    2014-08-01

    Bimetallic nanoparticles, enclosed by high-index facets, have great catalytic activity and selectivity owing to the synergy effects of high-index facets and the electronic structures of alloy. In this paper, a discrete particle swarm optimization algorithm was employed to systematically investigate the structural stability and features of tetrahexahedral Pt-based bimetallic nanoparticles with high-index facets. Different Pt/Ag, Pt/Cu, Pt/Pd atom ratios and particle sizes were considered in this work. The simulation results reveal that these alloy nanoparticles exhibit considerably different structural characteristics. Pt-Ag nanoparticles tend to form Pt-Ag core-shell structure. Pt-Cu nanoparticles are preferred to take multi-shell structure with Cu on the outer surface while Pt-Pd nanoparticles present a mixing structure in the interior and Pd-dominated surface. Atomic distribution and bonding characteristics were applied to further characterize the structural features of Pt-based nanoparticles. This study provides an important insight into the structural stability and features of Pt-based nanoparticles with different alloys.

  16. Origin of synergistic effect over Ni-based bimetallic surfaces: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Fan, Chen; Zhu, Yi-An; Xu, Yue; Zhou, Yan; Zhou, Xing-Gui; Chen, De

    2012-07-01

    Density functional theory calculations have been conducted to explore the physical origin of the synergistic effect over Ni-based surface alloys using methane dissociation as a probe reaction. Some late transition metal atoms (M = Cu, Ru, Rh, Pd, Ag, Pt, and Au) are substituted for surface Ni atoms to examine the variation in electronic structure and adsorption property of Ni(111). Two types of threefold hollow sites, namely, the Ni2M and Ni3 sites, are taken into account. The calculated results indicate that the variation in the CHx adsorption energy at the Ni2M and Ni3 sites is dominated by the ensemble and ligand effect, respectively, and the other factors such as surface and adsorbate distortion and electrostatic interaction affect the catalytic properties of the bimetallic surfaces to a smaller extent. Both the Brønsted-Evans-Polanyi relationship and the scaling correlation hold true on the Ni-based bimetallic surfaces. With the combination of these two linear energy relations, the corrected binding energy of atomic C is found to be a good descriptor for representing the catalytic activity of the alloyed surfaces. Considering the compromise between the catalytic activity and catalyst stability, we suggest that the Rh/Ni catalyst is a good candidate for methane dissociation.

  17. Photochemical synthesis of mono and bimetallic nanoparticles and their use in catalysis

    NASA Astrophysics Data System (ADS)

    Pardoe, Andrea

    2011-07-01

    Nanomaterials have become a popular topic of research over the years because of their many important applications. It can be a challenge to stabilize the particles at a nanometer size, while having control over their surface features. Copper nanoparticles were synthesized photochemically using a photogenerated radical allowing spatial and temporal control over their formation. The synthesis was affected by the stabilizers used, which changed the size, dispersity, rate of formation, and oxidation rate. Copper nanoparticles suffer from their fast oxidation in air, so copper-silver bimetallic nanoparticles were synthesized in attempts to overcome the oxidation of copper nanoparticles. Bimetallic nanoparticles were synthesized, but preventing the oxidation of the copper nanoparticles proved difficult. One important application of nanoparticles that was explored here is in catalyzing organic reactions. Because of the fast oxidation of copper nanoparticles, silver nanoparticles were synthesized photochemically on different supports including TiO2 and hydrotalcite (HTC). Their catalytic efficiency was tested using alcohol oxidations. Different silver nanoparticle shapes (decahedra and plates) were compared with the spheres to see the different catalytic efficiencies.

  18. Catalytically Active Bimetallic Nanoparticles Supported on Porous Carbon Capsules Derived From Metal-Organic Framework Composites.

    PubMed

    Yang, Hui; Bradley, Siobhan J; Chan, Andrew; Waterhouse, Geoffrey I N; Nann, Thomas; Kruger, Paul E; Telfer, Shane G

    2016-09-14

    We report a new methodology for producing monometallic or bimetallic nanoparticles confined within hollow nitrogen-doped porous carbon capsules. The capsules are derived from metal-organic framework (MOF) crystals that are coated with a shell of a secondary material comprising either a metal-tannic acid coordination polymer or a resorcinol-formaldehyde polymer. Platinum nanoparticles are optionally sandwiched between the MOF core and the shell. Pyrolysis of the MOF-shell composites produces hollow capsules of porous nitrogen-doped carbon that bear either monometallic (Pt, Co, and Ni) or alloyed (PtCo and PtNi) metal nanoparticles. The Co and Ni components of the bimetallic nanoparticles are derived from the shell surrounding the MOF crystals. The hollow capsules prevent sintering and detachment of the nanoparticles, and their porous walls allow for efficient mass transport. Alloyed PtCo nanoparticles embedded in the capsule walls are highly active, selective, and recyclable catalysts for the hydrogenation of nitroarenes to anilines. PMID:27575666

  19. Designing Pd-on-Au bimetallic nanoparticle catalysts for trichloroethene hydrodechlorination.

    PubMed

    Nutt, Michael O; Hughes, Joseph B; Michael, S Wong

    2005-03-01

    Alumina-supported palladium (Pd) catalysts have previously been shown to hydrodechlorinate trichloroethene (TCE) and other chlorinated compounds in water, at room temperature, and in the presence of hydrogen. The feasibility of this catalytic technology to remediate groundwater of halogenated compounds can be improved by re-designing the Pd material in order to increase catalytic activity. We synthesized and characterized Pd supported on gold nanoparticles (Au NPs) of different Pd loadings. In all cases, we found that these catalysts were considerably more active than Pd NPs, alumina-supported Pd, ard Pd-black (62.0, 12.2, and 0.42 L x g(Pd)(-1) x min(-1), respectively). There is a synergistic effect of the Pd-on-Au bimetallic structure, with the material with the highest TCE hydrodechlorination activity (943 L x g(Pd)(-1) x min(-1)) comprised of Au NPs partially covered by Pd metal. The Pd-on-Au bimetallic catalyst structure provides a new synthesis approach in improving the catalytic properties of monometallic Pd materials. The resulting nanoparticle-based materials should be highly suitable as hydrodehalogenation and reduction catalysts for the remediation of various organic and inorganic groundwater contaminants.

  20. Repairable, nanostructured biomimetic hydrogels

    NASA Astrophysics Data System (ADS)

    Firestone, M.; Brombosz, S.; Grubjesic, S.

    2013-03-01

    Proteins facilitate many key cellular processes, including signal recognition and energy transduction. The ability to harness this evolutionarily-optimized functionality could lead to the development of protein-based systems useful for advancing alternative energy storage and conversion. The future of protein-based, however, requires the development of materials that will stabilize, order and control the activity of the proteins. Recently we have developed a synthetic approach for the preparation of a durable biomimetic chemical hydrogel that can be reversibly swollen in water. The matrix has proven ideal for the stable encapsulation of both water- and membrane-soluble proteins. The material is composed of an aqueous dispersion of a diacrylate end-derivatized PEO-PPO-PEO macromer, a saturated phospholipid and a zwitterionic co-surfactant that self-assembles into a nanostructured physical gel at room temperature as determined by X-ray scattering. The addition of a water soluble PEGDA co-monomer and photoinitator does not alter the self-assembled structure and UV irradiation serves to crosslink the acrylate end groups on the macromer with the PEGDA forming a network within the aqueous domains as determined by FT-IR. More recently we have begun to incorporate reversible crosslinks employing Diels-Alder chemistry, allowing for the extraction and replacement of inactive proteins. The ability to replenish the materials with active, non-denatured forms of protein is an important step in advancing these materials for use in nanostructured devices This work was supported by the Office of Basic Energy Sciences, Division of Materials Sciences, USDoE under Contract No. DE-AC02-06CH11357.

  1. Efficient solvent-free hydrogenation of ketones over flame-prepared bimetallic Pt-Pd/ZrO(2) catalysts.

    PubMed

    Jiang, Yijiao; Büchel, Robert; Huang, Jun; Krumeich, Frank; Pratsinis, Sotiris E; Baiker, Alfons

    2012-07-01

    Named and flamed: Bimetallic Pt-Pd/ZrO(2) catalysts with different Pt/Pd atomic ratios and high dispersion of the metal nanoparticles are prepared by a single-step flame-spray pyrolysis. The catalysts show excellent activity and tunable product selectivity for the solvent-free hydrogenation of the ketone model compounds cyclopentanone and acetophenone. PMID:22674738

  2. Core-shell Rh-Pt nanocubes: A model for studying compressive strain effects in bimetallic nanocatalysts

    NASA Astrophysics Data System (ADS)

    Harak, Ethan William

    Shape-controlled bimetallic nanocatalysts often have increased activities and stabilities over their monometallic counterparts due to surface strain effects and electron transfer between the two metals. Here, we demonstrate that the degree of surface strain can be manipulated in shape-controlled nanocrystals through a bimetallic core shell architecture. This ability is achieved in a model core shell Rh Pt nanocube system through control of shell thickness. An increase in the Pt shell thickness leads to more compressive strain, which can increase the Pt 4f7/2 binding energy by as much as 0.13 eV. This change in electronic structure is correlated with a weakening of surface-adsorbate interactions, which we exploit to reduce catalyst poisoning by CO during formic acid electrooxidation. In fact, by precisely controlling the Pt shell thickness, the maximum current density achieved with Rh Pt nanocubes was 3.5 times greater than that achieved with similarly sized Pt nanocubes, with decreased CO generation as well. This system serves as a model for how bimetallic architectures can be used to manipulate the electronic structure of nanoparticle surfaces for efficient catalysis. The strategy employed here should enable the performance of bimetallic nanomaterials comprised of more cost-effective metals to be enhanced as well.

  3. Characterization of Na+- beta-Zeolite Supported Pd and Pd Ag Bimetallic Catalysts using EXAFS, TEM and Flow Reactor

    SciTech Connect

    Huang,W.; Lobo, R.; Chen, J.

    2008-01-01

    Flow reactor studies of the selective hydrogenation of acetylene in the presence of ethylene have been performed on Na+ exchanged {beta}-zeolite supported Pd, Ag and PdAg catalysts, as an extension of our previous batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40-51]. Results from flow reactor studies show that the PdAg/Na+-{beta}-zeolite bimetallic catalyst has lower activity than Pd/Na+-{beta}-zeolite monometallic catalyst, while Ag/Na+-{beta}-zeolite does not show any activity for acetylene hydrogenation. However, the selectivity for the PdAg bimetallic catalyst is much higher than that for either the Pd catalyst or Ag catalyst. The selectivity to byproduct (ethane) is greatly inhibited on the PdAg bimetallic catalyst as well. The results from the current flow reactor studies confirmed the pervious results from batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40-51]. In addition, we used transmission electron microscope (TEM), extended X-ray absorption fine structure (EXAFS), and FTIR of CO adsorption to confirm the formation of Pd-Ag bimetallic alloy in the PdAg/Na+-{beta}-zeolite catalyst.

  4. Synthesis of bimetallic Pt-Pd core-shell nanocrystals and their high electrocatalytic activity modulated by Pd shell thickness.

    PubMed

    Li, Yujing; Wang, Zhi Wei; Chiu, Chin-Yi; Ruan, Lingyan; Yang, Wenbing; Yang, Yang; Palmer, Richard E; Huang, Yu

    2012-02-01

    Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50 mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more resistant to the CO poisoning than Pt NCs and Pt black. It is also demonstrated that the bimetallic Pt-Pd core-shell NCs can enhance the current density of the methanol oxidation reaction, lowering the over-potential by 35 mV with respect to the Pt core NCs. Further investigation reveals that the Pd/Pt ratio of 1/3, which corresponds to nearly monolayer Pd deposition on Pt core NCs, gives the highest oxidation current density and lowest over-potential. This study shows for the first time the systematic investigation of effects of Pd atomic shells on Pt-Pd bimetallic nanocatalysts, providing valuable guidelines for designing high-performance catalysts for fuel cell applications. PMID:22159178

  5. Final Technical Report: First Principles Investigations for the Ensemble Effects of PdAu and PtAu Bimetallic Nanocatalysts

    SciTech Connect

    Ruqian Wu

    2012-05-18

    Bimetallic surfaces with tunable chemical properties have attracted broad attention in recent years due to their ample potential for heterogeneous catalysis applications. The local chemical properties of constituents are strongly altered from their parent metals by 'ligand effect', a term encompassing the influences of charge transfer, orbital rehybridization and lattice strain. In comparison to the aforementioned, the 'ensemble effect' associated with particular arrangements of the active constituents have received much less attention, despite their notable importance towards the determination of reactivity and selectivity of bimetallic catalysts. We performed theoretical studies for understanding the ensemble effects on bimetallic catalysis: (i) simulations for the formation of different ensembles on PdAu and PtAu nanoclusters; (ii) studies of the size, shape, and substrate dependence of their electronic properties; and (iii) simulations for model reactions such as CO oxidation, methanol, ethylene and water dehydrogenation on PdAu and PtAu nanoclusters. In close collaboration with leading experimental groups, our theoretical research elucidated the fundamentals of Au based bimetallic nanocatalysts.

  6. Removal of trichloroethylene DNAPL trapped in porous media using nanoscale zerovalent iron and bimetallic nanoparticles: direct observation and quantification.

    PubMed

    Wang, Qiliang; Jeong, Seung-Woo; Choi, Heechul

    2012-04-30

    Direct trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) removal inside pore areas using nanoscale zerovalent iron (NZVI) and bimetallic nanoparticles were first investigated in a water-saturated porous glass micromodel. Effects of nitrate, aqueous ethanol co-solvent, humic substance, and elapsed time on TCE DNAPL removal using NZVI were studied by direct visualization. The removal efficiency was then quantified by directly measuring the remaining TCE DNAPL blobs area using an image analyzer. As ethanol content of co-solvent increased, TCE DNAPL removal by NZVI was also increased implying sequential TCE DNAPL removal mechanisms: as dissolved TCE was degraded by NZVI, TCE dissolution from TCE blobs would be then facilitated and the TCE blob areas would be eventually reduced. The presence of nitrate and humic substance hindered the NZVI reactivity for the TCE DNAPL removal. In contrast, the TCE DNAPL removal efficiency was enhanced using bimetallic nanoparticles in a short-term reaction by generating atomic hydrogen for catalytic hydro-dechlorination. However, all TCE DNAPL removal efficiencies reached the same level after long-term reaction using both NZVI and bimetallic nanoparticles. Direct TCE DNAPL observation clearly implied that TCE blobs existed for long time even though all TCE blobs were fully exposed to NZVI and bimetallic nanoparticles.

  7. Nanostructured Materials for Renewable Energy

    SciTech Connect

    2009-11-01

    This factsheet describes a research project whose overall objective is to advance the fundamental understanding of novel photoelectronic organic device structures integrated with inorganic nanostructures, while also expanding the general field of nanomaterials for renewable energy devices and systems.

  8. NiW and NiRu Bimetallic Catalysts for Ethylene Steam Reforming: Alternative Mechanisms for Sulfur Resistance

    SciTech Connect

    Rangan, M.; Yung, M. M.; Medlin, J. W.

    2012-06-01

    Previous investigations of Ni-based catalysts for the steam reforming of hydrocarbons have indicated that the addition of a second metal can reduce the effects of sulfur poisoning. Two systems that have previously shown promise for such applications, NiW and NiRu, are considered here for the steam reforming of ethylene, a key component of biomass derived tars. Monometallic and bimetallic Al{sub 2}O{sub 3}-supported Ni and W catalysts were employed for ethylene steam reforming in the presence and absence of sulfur. The NiW catalysts were less active than Ni in the absence of sulfur, but were more active in the presence of 50 ppm H{sub 2}S. The mechanism for the W-induced improvements in sulfur resistance appears to be different from that for Ru in NiRu. To probe reasons for the sulfur resistance of NiRu, the adsorption of S and C{sub 2}H{sub 4} on several bimetallic NiRu alloy surfaces ranging from 11 to 33 % Ru was studied using density functional theory (DFT). The DFT studies reveal that sulfur adsorption is generally favored on hollow sites containing Ru. Ethylene preferentially adsorbs atop the Ru atom in all the NiRu (111) alloys investigated. By comparing trends across the various bimetallic models considered, sulfur adsorption was observed to be correlated with the density of occupied states near the Fermi level while C{sub 2}H{sub 4} adsorption was correlated with the number of unoccupied states in the d-band. The diverging mechanisms for S and C{sub 2}H{sub 4} adsorption allow for bimetallic surfaces such as NiRu that enhance ethylene binding without accompanying increases in sulfur binding energy. In contrast, bimetallics such as NiSn and NiW appear to decrease the affinity of the surface for both the reagent and the poison.

  9. Chemically enabled nanostructure fabrication

    NASA Astrophysics Data System (ADS)

    Huo, Fengwei

    The first part of the dissertation explored ways of chemically synthesizing new nanoparticles and biologically guided assembly of nanoparticle building blocks. Chapter two focuses on synthesizing three-layer composite magnetic nanoparticles with a gold shell which can be easily functionalized with other biomolecules. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding properties of gold nanoparticle probes, while maintaining the magnetic properties of the Fe3O4 inner shell. Chapter three describes a new method for synthesizing nanoparticles asymmetrically functionalized with oligonucleotides and the use of these novel building blocks to create satellite structures. This synthetic capability allows one to introduce valency into such structures and then use that valency to direct particle assembly events. The second part of the thesis explored approaches of nanostructure fabrication on substrates. Chapter four focuses on the development of a new scanning probe contact printing method, polymer pen lithography (PPL), which combines the advantages of muCp and DPN to achieve high-throughput, flexible molecular printing. PPL uses a soft elastomeric tip array, rather than tips mounted on individual cantilevers, to deliver inks to a surface in a "direct write" manner. Arrays with as many as ˜11 million pyramid-shaped pens can be brought into contact with substrates and readily leveled optically in order to insure uniform pattern development. Chapter five describes gel pen lithography, which uses a gel to fabricate pen array. Gel pen lithography is a low-cost, high-throughput nanolithography method especially useful for biomaterials patterning and aqueous solution patterning which makes it a supplement to DPN and PPL. Chapter 6 shows a novel form of optical nanolithography, Beam Pen Lithography (BPL), which uses an array of NSOM pens to do nanoscale optical

  10. Catalytic Sorption of (Chloro)Benzene and Napthalene in Aqueous Solutions by Granular Activated Carbon Supported Bimetallic Iron and Palladium Nanoparticles

    EPA Science Inventory

    Adsorption of benzene, chlorobenzene, and naphthalene on commercially available granular activated carbon (GAC) and bimetallic nanoparticle (Fe/Pd) loaded GAC was investigated for the potential use in active capping of contaminated sediments. Freundlich and Langmuir linearizatio...

  11. Structural, electronic and magnetic properties of pure metallic and bimetallic nanoclusters: Empirical and density functional studies

    NASA Astrophysics Data System (ADS)

    Hijazi, Iyad Ahmed

    This thesis is aimed at investigating structural, electronic and magnetic properties of metallic/bimetallic nanoclusters. First, a simple empirical embedded-atom potential (EAM) that includes a long range force is developed for FCC metals and alloys. The proposed potential for pure metals does not require modification of the initial function form when being applied to alloy systems. The potential parameters are determined by fitting lattice constant, three elastic constants, cohesive energy, and vacancy formation energies of the pure metals, and the heats of solution of the binary alloys via an optimization technique. Parameters for Ag, Al, Au, Cu, Ni, Pd and Pt have been obtained and used to calculate the bulk modulus, divacancy formation energy, crystal stability, stacking fault energy, vacancy migration energy, and melting point for each pure metal and the heats of formation and lattice constants for binary alloys. The predicted values are in good agreement with experimental results. Structural stabilities and energetics for Cu and Au clusters with up to 56 atoms were also studied using a hierarchical search method. The method employed an effective Monte Carlo (MC) simulated annealing method, utilizing our EAM potential, to identify low-lying structures. In general agreement with previous empirical studies, the lowest-energy copper structures adapt a single icosahedral structural motif. However, contrary to studies that describe gold as less symmetric, this work demonstrates that gold clusters adapt both an icosahedral and icositetrahedral structural motifs with many clusters having symmetric geometries. The structures of the lowest-energy isomers were later optimized using Density Functional Theory (DFT) simulations, and compared to those of available clusters from previous studies. Their lowest-energy structures are mostly found in our pool of isomers, identified by the present method. Our results are in agreement with or lower in energy than existing ab

  12. CATALYSIS SCIENCE INITIATIVE: From First Principles Design to Realization of Bimetallic Catalysts for Enhanced Selectivity

    SciTech Connect

    MAVRIKAKIS, MANOS DUMESIC, JAMES A.

    2007-05-03

    In this project, we have integrated state-of-the-art Density Functional Theory (DFT) models of heterogeneous catalytic processes with high-throughput screening of bimetallic catalytic candidates for important industrial problems. We have studied a new class of alloys characterized by a surface composition different from the bulk composition, and investigated their stability and activity for the water-gas shift reaction and the oxygen reduction reaction. The former reaction is an essential part of hydrogen production; the latter is the rate-limiting step in low temperature H2 fuel cells. We have identified alloys that have remarkable stability and activity, while having a much lower material cost for both of these reactions. Using this knowledge of bimetallic interactions, we have also made progress in the industrially relevant areas of carbohydrate reforming and conversion of biomass to liquid alkanes. One aspect of this work is the conversion of glycerol (a byproduct of biodiesel production) to synthesis gas. We have developed a bifunctional supported Pt catalyst that can cleave the carbon-carbon bond while also performing the water-gas shift reaction, which allows us to better control the H2:CO ratio. Knowledge gained from the theoretical metal-metal interactions was used to develop bimetallic catalysts that perform this reaction at low temperature, allowing for an efficient coupling of this endothermic reaction with other reactions, such as Fischer-Tropsch or methanol synthesis. In our work on liquid alkane production from biomass, we have studied deactivation and selectivity in these areas as a function of metal-support interactions and reaction conditions, with an emphasis on the bifunctionality of the catalysts studied. We have identified a stable, active catalyst for this process, where the selectivity and yield can be controlled by the reaction conditions. While complete rational design of catalysts is still elusive, this work demonstrates the power of

  13. Strategies for designing supported gold-palladium bimetallic catalysts for the direct synthesis of hydrogen peroxide.

    PubMed

    Edwards, Jennifer K; Freakley, Simon J; Carley, Albert F; Kiely, Christopher J; Hutchings, Graham J

    2014-03-18

    Hydrogen peroxide is a widely used chemical but is not very efficient to make in smaller than industrial scale. It is an important commodity chemical used for bleaching, disinfection, and chemical manufacture. At present, manufacturers use an indirect process in which anthraquinones are sequentially hydrogenated and oxidized in a manner that hydrogen and oxygen are never mixed. However, this process is only economic at a very large scale producing a concentrated product. For many years, the identification of a direct process has been a research goal because it could operate at the point of need, producing hydrogen peroxide at the required concentration for its applications. Research on this topic has been ongoing for about 100 years. Until the last 10 years, catalyst design was solely directed at using supported palladium nanoparticles. These catalysts require the use of bromide and acid to arrest peroxide decomposition, since palladium is a very active catalyst for hydrogen peroxide hydrogenation. Recently, chemists have shown that supported gold nanoparticles are active when gold is alloyed with palladium because this leads to a significant synergistic enhancement in activity and importantly selectivity. Crucially, bimetallic gold-based catalysts do not require the addition of bromide and acids, but with carbon dioxide as a diluent its solubility in the reaction media acts as an in situ acid promoter, which represents a greener approach for peroxide synthesis. The gold catalysts can operate under intrinsically safe conditions using dilute hydrogen and oxygen, yet these catalysts are so active that they can generate peroxide at commercially significant rates. The major problem associated with the direct synthesis of hydrogen peroxide concerns the selectivity of hydrogen usage, since in the indirect process this factor has been finely tuned over decades of operation. In this Account, we discuss how the gold-palladium bimetallic catalysts have active sites for the

  14. Kinetics and mechanism of the liquid-phase oxidation of cyclohexene. IV. Decomposition of cyclohexenyl hydroperoxide in the presence of bimetallic catalysts

    SciTech Connect

    Baevskii, M.Yu.; Litvintsev, I.Yu.; Sapunov, V.N.

    1988-11-01

    The kinetic principles of the decomposition of cyclohexenyl hydroperoxide in cyclohexene solution in homogeneous catalysis by vanadium-containing bimetallic systems were investigated. For Co-V and Pb-V, the formation of complexes with low activity in catalysis was demonstrated by kinetic and spectral methods. A mathematical model was obtained for the process, adequately describing the conversions of cyclohexenyl hydroperoxide in the presence of bimetallic systems.

  15. Topological crystalline insulator nanostructures.

    PubMed

    Shen, Jie; Cha, Judy J

    2014-11-01

    Topological crystalline insulators are topological insulators whose surface states are protected by the crystalline symmetry, instead of the time reversal symmetry. Similar to the first generation of three-dimensional topological insulators such as Bi₂Se₃ and Bi₂Te₃, topological crystalline insulators also possess surface states with exotic electronic properties such as spin-momentum locking and Dirac dispersion. Experimentally verified topological crystalline insulators to date are SnTe, Pb₁-xSnxSe, and Pb₁-xSnxTe. Because topological protection comes from the crystal symmetry, magnetic impurities or in-plane magnetic fields are not expected to open a gap in the surface states in topological crystalline insulators. Additionally, because they have a cubic structure instead of a layered structure, branched structures or strong coupling with other materials for large proximity effects are possible, which are difficult with layered Bi₂Se₃ and Bi₂Te₃. Thus, additional fundamental phenomena inaccessible in three-dimensional topological insulators can be pursued. In this review, topological crystalline insulator SnTe nanostructures will be discussed. For comparison, experimental results based on SnTe thin films will be covered. Surface state properties of topological crystalline insulators will be discussed briefly.

  16. Nanostructured Interfaces for Thermoelectrics

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Marconnet, A. M.; Panzer, M. A.; Leblanc, S.; Dogbe, S.; Ezzahri, Y.; Shakouri, A.; Goodson, K. E.

    2010-09-01

    Temperature drops at the interfaces between thermoelectric materials and the heat source and sink reduce the overall efficiency of thermoelectric systems. Nanostructured interfaces based on vertically aligned carbon nanotubes (CNTs) promise the combination of mechanical compliance and high thermal conductance required for thermoelectric modules, which are subjected to severe thermomechanical stresses. This work discusses the property require- ments for thermoelectric interface materials, reviews relevant data available in the literature for CNT films, and characterizes the thermal properties of vertically aligned multiwalled CNTs grown on a candidate thermoelectric material. Nanosecond thermoreflectance thermometry provides thermal property data for 1.5- μm-thick CNT films on SiGe. The thermal interface resistances between the CNT film and surrounding materials are the dominant barriers to thermal transport, ranging from 1.4 m2 K MW-1 to 4.3 m2 K MW-1. The volumetric heat capacity of the CNT film is estimated to be 87 kJ m-3 K-1, which corresponds to a volumetric fill fraction of 9%. The effect of 100 thermal cycles from 30°C to 200°C is also studied. These data provide the groundwork for future studies of thermoelectric materials in contact with CNT films serving as both a thermal and electrical interface.

  17. Phonon engineering for nanostructures.

    SciTech Connect

    Aubry, Sylvie; Friedmann, Thomas Aquinas; Sullivan, John Patrick; Peebles, Diane Elaine; Hurley, David H.; Shinde, Subhash L.; Piekos, Edward Stanley; Emerson, John Allen

    2010-01-01

    Understanding the physics of phonon transport at small length scales is increasingly important for basic research in nanoelectronics, optoelectronics, nanomechanics, and thermoelectrics. We conducted several studies to develop an understanding of phonon behavior in very small structures. This report describes the modeling, experimental, and fabrication activities used to explore phonon transport across and along material interfaces and through nanopatterned structures. Toward the understanding of phonon transport across interfaces, we computed the Kapitza conductance for {Sigma}29(001) and {Sigma}3(111) interfaces in silicon, fabricated the interfaces in single-crystal silicon substrates, and used picosecond laser pulses to image the thermal waves crossing the interfaces. Toward the understanding of phonon transport along interfaces, we designed and fabricated a unique differential test structure that can measure the proportion of specular to diffuse thermal phonon scattering from silicon surfaces. Phonon-scale simulation of the test ligaments, as well as continuum scale modeling of the complete experiment, confirmed its sensitivity to surface scattering. To further our understanding of phonon transport through nanostructures, we fabricated microscale-patterned structures in diamond thin films.

  18. The nanostructure problem

    SciTech Connect

    Billinge, S.

    2010-03-22

    Diffraction techniques are making progress in tackling the difficult problem of solving the structures of nanoparticles and nanoscale materials. The great gift of x-ray crystallography has made us almost complacent in our ability to locate the three-dimensional coordinates of atoms in a crystal with a precision of around 10{sup -4} nm. However, the powerful methods of crystallography break down for structures in which order only extends over a few nanometers. In fact, as we near the one hundred year mark since the birth of crystallography, we face a resilient frontier in condensed matter physics: our inability to routinely and robustly determine the structure of complex nanostructured and amorphous materials. Knowing the structure and arrangement of atoms in a solid is so fundamental to understanding its properties that the topic routinely occupies the early chapters of every solid-state physics textbook. Yet what has become clear with the emergence of nanotechnology is that diffraction data alone may not be enough to uniquely solve the structure of nanomaterials. As part of a growing effort to incorporate the results of other techniques to constrain x-ray refinements - a method called 'complex modeling' which is a simple but elegant approach for combining information from spectroscopy with diffraction data to solve the structure of several amorphous and nanostructured materials. Crystallography just works, so we rarely question how and why this is so, yet understanding the physics of diffraction can be very helpful as we consider the nanostructure problem. The relationship between the electron density distribution in three dimensions (i.e., the crystal structure) and an x-ray diffraction pattern is well established: the measured intensity distribution in reciprocal space is the square of the Fourier transform of the autocorrelation function <{rho}(r){rho}(r+r')> of the electron density distribution {rho}(r). The fact that we get the autocorrelation function

  19. Reaction pathways of model compounds of biomass-derived oxygenates on Fe/Ni bimetallic surfaces

    NASA Astrophysics Data System (ADS)

    Yu, Weiting; Chen, Jingguang G.

    2015-10-01

    Controlling the activity and selectivity of converting biomass-derivatives to fuels and valuable chemicals is critical for the utilization of biomass feedstocks. There are primarily three classes of non-food competing biomass, cellulose, hemicellulose and lignin. In the current work, glycolaldehyde, furfural and acetaldehyde are studied as model compounds of the three classes of biomass-derivatives. Monometallic Ni(111) and monolayer (ML) Fe/Ni(111) bimetallic surfaces are studied for the reaction pathways of the three biomass surrogates. The ML Fe/Ni(111) surface is identified as an efficient surface for the conversion of biomass-derivatives from the combined results of density functional theory (DFT) calculations and temperature programmed desorption (TPD) experiments. A correlation is also established between the optimized adsorption geometry and experimental reaction pathways. These results should provide helpful insights in catalyst design for the upgrading and conversion of biomass.

  20. Dual Wavelength Laser Writing and Measurement Methodology for High Resolution Bimetallic Grayscale Photomasks

    NASA Astrophysics Data System (ADS)

    Qarehbaghi, Reza

    Grayscale bimetallic photomasks consist of bi-layer thermal resists (Bismuth-on-Indium or Tin-on-Indium) which become controllably transparent when exposed to a focused laser beam as a function of the absorbed power changing from ~3OD (unexposed) to <0.22OD (fully exposed). To achieve high accuracy grayscale pattern, the OD must be measured and controlled while writing. This thesis investigates using two wavelength beams for mask writing (514.5nm) and OD measurement (457.9nm) separated from a multi-line Argon ion laser source: a Dual Wavelength Writing and Measurement System. The writing laser profile was modified to a top-hat using a beam shaper. Several mask patterns tested the creation of high resolution grayscale masks. Finally, for creation of 3D structures in photoresist, the mask transparency to resist thickness requirements was formulated and linear slope patterns were successfully created.

  1. Synthesis of homogeneous Pt-bimetallic nanoparticles as highly efficient electrocatalysts.

    SciTech Connect

    Wang, C.; Chi, M.; Li, D.; van der Vliet, D.; Wang, G.; Lin, Q.; Mitchell, J.; More, K. L.; Markovic, N. M.; Stamenkovic, V. R.

    2011-01-01

    Alloying has shown enormous potential for tailoring the atomic and electronic structures, and improving the performance of catalytic materials. Systematic studies of alloy catalysts are, however, often compromised by inhomogeneous distribution of alloying components. Here we introduce a general approach for the synthesis of monodispersed and highly homogeneous Pt-bimetallic alloy nanocatalysts. Pt{sub 3}M (where M = Fe, Ni, or Co) nanoparticles were prepared by an organic solvothermal method and then supported on high surface area carbon. These catalysts attained a homogeneous distribution of elements, as demonstrated by atomic-scale elemental analysis using scanning transmission electron microscopy. They also exhibited high catalytic activities for the oxygen reduction reaction (ORR), with improvement factors of 2-3 versus conventional Pt/carbon catalysts. The measured ORR catalytic activities for Pt{sub 3}M nanocatalysts validated the volcano curve established on extended surfaces, with Pt{sub 3}Co being the most active alloy.

  2. Development of bi-metallic Fe-Bi nanocomposites: synthesis and characterization.

    PubMed

    Mattei, J G; Pelletier, F; Ciuculescu, D; Lecante, P; Amiens, C; Casanove, M J

    2012-11-01

    We investigate the formation of bi-metallic particles in the Fe-Bi system, well known as totally immiscible in the bulk, using a large combination of structural and element-sensitive techniques, well-adapted to the nanoscale. The synthesis approach makes use of the kinetics of decomposition of the different precursors to achieve a controlled sequential growth of the different elements. Different ligands have also been used in order to limit the size and ensure dispersion of the synthesized particles. Our results give evidence for the presence of body-centered cubic ferromagnetic iron nanograins together with larger bismuth crystallites. Interestingly, while the iron particles remain very small, the resistance to oxidation of the Fe-Bi nanocomposites highly depends on the stabilizing ligand used in the synthesis. The presence of both metals, Fe and Bi, in a single cluster has been clearly revealed in the oxidation resistant composite synthesized using the HMDS ligand.

  3. Sophisticated Design of Covalent Organic Frameworks with Controllable Bimetallic Docking for a Cascade Reaction.

    PubMed

    Leng, Wenguang; Peng, Yongsheng; Zhang, Jianqiang; Lu, Hui; Feng, Xiao; Ge, Rile; Dong, Bin; Wang, Bo; Hu, Xiangping; Gao, Yanan

    2016-06-27

    Precise control of the number and position of the catalytic metal ions in heterogeneous catalysts remains a big challenge. Here we synthesized a series of two-dimensional (2D) covalent organic frameworks (COFs) containing two different types of nitrogen ligands, namely imine and bipyridine, with controllable contents. For the first time, the selective coordination of the two nitrogen ligands of the 2D COFs to two different metal complexes, chloro(1,5-cyclooctadiene)rhodium(I) (Rh(COD)Cl) and palladium(II) acetate (Pd(OAc)2 ), has been realized using a programmed synthetic procedure. The bimetallically docked COFs showed excellent catalytic activity in a one-pot addition-oxidation cascade reaction. The high surface area, controllable metal-loading content, and predesigned active sites make them ideal candidates for their use as heterogeneous catalysts in a wide range of chemical reactions.

  4. High-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles for phenol hydrogenation

    NASA Astrophysics Data System (ADS)

    Huang, Chao; Yang, Xu; Yang, Hui; Huang, Peiyan; Song, Huiyu; Liao, Shijun

    2014-10-01

    A high-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles (MSN), PdRu/MSN, was prepared by a facile impregnation-hydrogen reduction method. It was found that PdRu/MSN showed 5 times higher activity than that of Pd/MSN towards the liquid-phase hydrogenation of phenol. The catalysts were characterized comprehensively by multiple techniques, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature program reduction (TPR). It was revealed that adding Ru could effectively improve the Pd dispersion and promote the electronic interaction between the Pd and Ru, both of which contribute to enhancing the catalytic activity.

  5. Nickel-cobalt bimetallic anode catalysts for direct urea fuel cell

    PubMed Central

    Xu, Wei; Zhang, Huimin; Li, Gang; Wu, Zucheng

    2014-01-01

    Nickel is an ideal non-noble metal anode catalyst for direct urea fuel cell (DUFC) due to its high activity. However, there exists a large overpotential toward urea electrooxidation. Herein, NiCo/C bimetallic nanoparticles were prepared with various Co contents (0, 10, 20, 30 and 40 wt%) to improve the activity. The best Co ratio was 10% in the aspect of cell performance, with a maximum power density of 1.57 mW cm−2 when 0.33 M urea was used as fuel, O2 as oxidant at 60°C. The effects of temperature and urea concentration on DUFC performance were investigated. Besides, direct urine fuel cell reaches a maximum power density of 0.19 mW cm−2 with an open circuit voltage of 0.38 V at 60°C. PMID:25168632

  6. Bioacid hydroconversion over Co, Ni, Cu Mono- and indium-doped bimetallic catalysts.

    PubMed

    Onyestyák, György; Harnos, Szabolcs; Kalló, Dénes

    2015-01-01

    Caprylic acid (CA) as model reactant was selectively reduced in a flow-through reactor in hydrogen stream at 21 bar total pressure and 240-360 °C over alumina loaded with the adjacent Co, Ni, Cu host and In guest metals. The main target of this research is the recognition of efficient cobalt catalysts for carboxylic group hydroconversion compared to more familiar nickel and copper composites. The catalysts were activated in H(2) flow at 21 bar and 450 °C. By variation of main metal or modification with indium, mono- or bimetallic catalysts can be obtained with low hydrodecarbonylation activity and high alcohol selectivity. These composites have higher hydrodeoxygenation (HDO) activity and alcohol selectivity than the conventional commercial catalysts applied for fatty alcohol production. Great variety of catalytic behavior indicates complexity of the surface reactions determined by several interacting factors.

  7. Ru-core/Cu-shell bimetallic nanoparticles with controlled size formed in one-pot synthesis.

    PubMed

    Helgadottir, I; Freychet, G; Arquillière, P; Maret, M; Gergaud, P; Haumesser, P H; Santini, C C

    2014-12-21

    Suspensions of bimetallic nanoparticles (NPs) of Ru and Cu have been synthesized by simultaneous decomposition of two organometallic compounds in an ionic liquid. These suspensions have been characterized by Anomalous Small-Angle X-ray Scattering (ASAXS) at energies slightly below the Ru K-edge. It is found that the NPs adopt a Ru-core, a Cu-shell structure, with a constant Ru core diameter of 1.9 nm for all Ru : Cu compositions, while the Cu shell thickness increases with Cu content up to 0.9 nm. The formation of RuCuNPs thus proceeds through rapid decomposition of the Ru precursor into RuNPs of constant size followed by the reaction of the Cu precursor and agglomeration as a Cu shell. Thus, the different decomposition kinetics of precursors make possible the elaboration of core-shell NPs composed of two metals without chemical affinity.

  8. Formation mechanism for the nanoscale amorphous interface in pulse-welded Al/Fe bimetallic systems

    NASA Astrophysics Data System (ADS)

    Li, Jingjing; Yu, Qian; Zhang, Zijiao; Xu, Wei; Sun, Xin

    2016-05-01

    Pulse or impact welding traditionally has been referred to as "solid-state" welding. By integrating advanced interface characterizations and diffusion calculations, we report that the nanoscale amorphous interface in the pulse-welded Al/Fe bimetallic system is formed by rapid heating and melting of a thin Al layer at the interface, diffusion of iron atoms in the liquid aluminum, and subsequent rapid quenching with diffused iron atoms in solution. This finding challenges the commonly held belief regarding the solid-state nature of the impact-based welding process for dissimilar metals. Elongated ultra-fine grains with high dislocation density and ultra-fine equiaxed grains also are observed in the weld interface vicinity on the steel and aluminum sides, respectively, which further confirms that melting and the subsequent recrystallization occurred on the aluminum side of the interface.

  9. Millimeter thick ionic polymer membrane-based IPMCs with bimetallic Pd-Pt electrodes

    NASA Astrophysics Data System (ADS)

    Palmre, Viljar; Kim, Sung Jun; Kim, Kwang

    2011-04-01

    Ionic polymer metal composites (IPMC) are a low-voltage driven Electroactive Polymers (EAP) that can be used as actuators or sensors. This paper presents a comparative study of millimeter thick ionic polymer membrane-based IPMCs with high-performance Pd-Pt electrodes and conventional Pt electrodes. IPMCs assembled with different electrodes are characterized in terms of electromechanical, -chemical and mechanolelectrical properties. The SEM and energy dispersive X-ray (EDS) analysis are used to investigate the distribution of deposited electrode metals in the cross-section of Pd-Pt IPMCs. The study shows that IPMCs assembled with millimeter thick ionic polymer membranes and bimetallic Pd-Pt electrodes are superior in mechanoelectrical sensing and, also, show considerably higher blocking forces compared to the conventional type of IPMCs. Blocking forces more than 30 grams are measured under 4V DC. However, the actuation response is slower than conventional IPMCs having approximately 0.2-0.3 mm thickness.

  10. Computational study of alkynes insertion into metal-hydride bonds catalyzed by bimetallic complexes.

    PubMed

    Di Tommaso, Stefania; Tognetti, Vincent; Sicilia, Emilia; Adamo, Carlo; Russo, Nino

    2010-11-01

    Density Functional Theory investigations on the insertion mechanism of phenylacetylene into metal-hydride bonds in bimetallic (Pt,Os) catalysts have been carried out. The results obtained have been also compared with the non-reactive monometallic (Os-based) system, to elucidate the cooperative effects and to explain the observed absence of reactivity. The identified reaction path involves phenylacetylene coordination followed by the insertion into the metal-hydride bond, leading to the formation of the experimentally observed products. Both steps do not require large energies compatible with the experimental conditions. The comparison with the reaction path for the monometallic species gives some hints on the cooperative effects due to the presence of the second metal which is related to its role in the CO release for creating a coordination site for phenylacetylene and not in the insertion energetics. The calculations provide a detailed analysis of the reaction complexity and provide a rationale for the efficiency of the process. PMID:20883042

  11. Bimetallic promotion of cooperative hydrogen transfer and heteroatom removal in coal liquefaction

    SciTech Connect

    Eisch, J.J.

    1991-10-01

    The ultimate objective of this research is to uncover new catalytic processes for the liquefaction of coal and for upgrading coal-derived fuels by removing undesirable organosulfur, organonitrogen and organooxygen constituents. Basic to both the liquefaction of coal and the purification of coal liquids is the transfer of hydrogen from such sources as dihydrogen, metal hydrides or partially reduced aromatic hydrocarbons to the extensive aromatic rings in coal itself or to aromatic sulfides, amines or ethers. Accordingly, this study is exploring how such crucial hydrogen-transfer processes might be catalyzed by soluble, low-valent transition metal complexes and/or Lewis acids under moderate conditions of temperature and pressure. By learning the mechanism whereby H{sub 2}, metal hydrides or partially hydrogenated aromatics do transfer hydrogen to model aromatic compounds, with the aid of homogeneous, bimetallic catalysts, we hope to identify new methods for producing superior fuels from coal.

  12. Nickel-cobalt bimetallic anode catalysts for direct urea fuel cell

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Zhang, Huimin; Li, Gang; Wu, Zucheng

    2014-08-01

    Nickel is an ideal non-noble metal anode catalyst for direct urea fuel cell (DUFC) due to its high activity. However, there exists a large overpotential toward urea electrooxidation. Herein, NiCo/C bimetallic nanoparticles were prepared with various Co contents (0, 10, 20, 30 and 40 wt%) to improve the activity. The best Co ratio was 10% in the aspect of cell performance, with a maximum power density of 1.57 mW cm-2 when 0.33 M urea was used as fuel, O2 as oxidant at 60°C. The effects of temperature and urea concentration on DUFC performance were investigated. Besides, direct urine fuel cell reaches a maximum power density of 0.19 mW cm-2 with an open circuit voltage of 0.38 V at 60°C.

  13. ORNL/MMES research into remedial applications of zero-valence metals. 2. Bimetallic enhancements

    SciTech Connect

    Korte, N.; Muftikian, R.; Grittini, C.

    1995-12-01

    Recent reports have described the dehalogenation of many low molecular weight chlorinated hydrocarbons with zero-valence iron. Batch, column, and preliminary field studies have suggested that elemental iron could play a significant role in the remediation of contaminated groundwater. However, available data suggested that the technique may be unsuitable for high concentrations of the dichloroethenes and vinly chloride. Moreover, little of no reaction was observed with dichloromethane. Consequently, several bimetallic systems have been evaluated as a means of increasing the rate of reaction in order to extend zero-valence metal reduction to a greater variety of systems containing chlorinated hydrocarbons. Laboratory studies demonstrated that the rate of dehalogenation of trichloroethene can be increased by two orders of magnitude with a co-metal. In addition, zero-valence metal reduction can be extended to dechlorination of less reactive compounds such as dichloromethane.

  14. Bi-Metallic Composite Structures With Designed Internal Residual Stress Field

    NASA Technical Reports Server (NTRS)

    Brice, Craig A.

    2014-01-01

    Shape memory alloys (SMA) have a unique ability to recover small amounts of plastic strain through a temperature induced phase change. For these materials, mechanical displacement can be accomplished by heating the structure to induce a phase change, through which some of the plastic strain previously introduced to the structure can be reversed. This paper introduces a concept whereby an SMA phase is incorporated into a conventional alloy matrix in a co-continuous reticulated arrangement forming a bi-metallic composite structure. Through memory activation of the mechanically constrained SMA phase, a controlled residual stress field is developed in the interior of the structure. The presented experimental data show that the memory activation of the SMA composite component significantly changes the residual stress distribution in the overall structure. Designing the structural arrangement of the two phases to produce a controlled residual stress field could be used to create structures that have much improved durability and damage tolerance properties.

  15. Numerical Simulation of the Proton Spin-Lattice Relaxation in Bimetallic Chain Compounds

    NASA Astrophysics Data System (ADS)

    Yamamoto, S.

    In response to recent proton spin relaxation-time measurements on a bimetallic chain compound NiCu(C7H6N2O6) (H2O)3\\cdot2H2O, we simulate the Raman relaxation process in Heisenberg alternating-spin chains on the assumption of predominantly dipolar hyperfine interactions between protons and magnetic ions. The relaxation time T1 is formulated within the spin-wave theory and is estimated as a function of temperature and an applied field H by a quantum Monte Carlo method. The low-temperature behavior of the relaxation rate T1-1 qualitatively varies with (S,s), while T1-1 is almost proportional to H-1/2 due to the characteristic dispersion relations.

  16. Competition by aquifer materials in a bimetallic nanoparticle/persulfate system for the treatment of trichloroethylene.

    PubMed

    Al-Shamsi, Mohammed Ahmad; Thomson, Neil R

    2013-10-01

    It has been suggested in the literature that aquifer materials can compete with the target organic compounds in an activated peroxygen system. In this study, we employed a rapid treatment method using persulfate activated with bimetallic nanoparticles to investigate the competition between aquifer materials and the dissolved phase of a target organic compound. The concentration of dissolved trichloroethylene (TCE) remaining after using the activated persulfate system was two- to three-fold higher in a soil slurry batch system than in an aqueous batch system. For all five aquifer materials investigated, an increase in the mass of the aquifer solids significantly decreased the degradation of TCE. A linear relationship was observed between the mass of aquifer materials and the initial TCE degradation rate, suggesting that the organic carbon and/or aquifer material constituents (e.g., carbonates and bicarbonates) compete with the oxidation of TCE.

  17. Synthesis of Co-based bimetallic nanocrystals with one-dimensional structure for selective control on syngas conversion

    NASA Astrophysics Data System (ADS)

    Ba, Rongbin; Zhao, Yonghui; Yu, Lujing; Song, Jianjun; Huang, Shuangshuang; Zhong, Liangshu; Sun, Yuhan; Zhu, Yan

    2015-07-01

    Co-based bimetallic nanocrystals with one-dimensional (1D) branches were synthesized by the heterogeneous nucleation of Co atoms onto prenucleated seeds, such as Pd or Cu, through a facile wet-chemical route. The peripheral branches (rod-like) of the Co-Pd and Co-Cu nanocrystals were outspread along the (001) direction and were enclosed by (101) facets. By switching the prenucleated metals to form robust Co-Pd or Co-Cu bimetallic nanocatalysts, the selectivity of CO hydrogenation could be adjusted purposely towards heavy paraffins, light olefins or oxygenates. The Anderson-Schulz-Flory chain-lengthening probabilities for products were up to 0.9 over Co-Pd nanocrystals, showing that long-chain hydrocarbons can be formed with high selectivity using the targeted design of Co-Pd nanocrystal catalysts. These Co-based bimetallic nanocrystals with a 1D structure exhibited superior catalytic activities over the corresponding Co-based nanoparticles for synthesis gas conversion.Co-based bimetallic nanocrystals with one-dimensional (1D) branches were synthesized by the heterogeneous nucleation of Co atoms onto prenucleated seeds, such as Pd or Cu, through a facile wet-chemical route. The peripheral branches (rod-like) of the Co-Pd and Co-Cu nanocrystals were outspread along the (001) direction and were enclosed by (101) facets. By switching the prenucleated metals to form robust Co-Pd or Co-Cu bimetallic nanocatalysts, the selectivity of CO hydrogenation could be adjusted purposely towards heavy paraffins, light olefins or oxygenates. The Anderson-Schulz-Flory chain-lengthening probabilities for products were up to 0.9 over Co-Pd nanocrystals, showing that long-chain hydrocarbons can be formed with high selectivity using the targeted design of Co-Pd nanocrystal catalysts. These Co-based bimetallic nanocrystals with a 1D structure exhibited superior catalytic activities over the corresponding Co-based nanoparticles for synthesis gas conversion. Electronic supplementary

  18. Key Physical Mechanisms in Nanostructured Solar Cells

    SciTech Connect

    Dr Stephan Bremner

    2010-07-21

    The objective of the project was to study both theoretically and experimentally the excitation, recombination and transport properties required for nanostructured solar cells to deliver energy conversion efficiencies well in excess of conventional limits. These objectives were met by concentrating on three key areas, namely, investigation of physical mechanisms present in nanostructured solar cells, characterization of loss mechanisms in nanostructured solar cells and determining the properties required of nanostructured solar cells in order to achieve high efficiency and the design implications.

  19. Complementary shapes in columnar liquid crystals: Structural control in homo- and heteronuclear bimetallic assemblies

    SciTech Connect

    Serrette, A.G.; Lai, C.K.; Swager, T.M.

    1994-12-01

    A comprehensive study of the liquid-crystalline properties of 51 bimetallic compounds based upon 1,3,5-triketonate and 1,3,5,7-tetraketonate ligands is reported. These materials are liquid crystalline when six or more side chains are appended to the mesogenic core, and only columnar phases were observed. Most of the liquid crystals were homonuclear dicopper complexes. Schiff-base derivatives of some of the triketones allowed for the synthesis of heteronuclear bimetallic liquid crystals. The NiCu and NiPd Schiff-base complexes are the first heteronuclear liquid crystals with proximate (strongly interacting) metal centers. Other heteronuclear complexes investigated were not liquid crystalline due to the tendency to retain coordinated solvent or to form strongly associated structures in the absence of axial ligands. The use of complementary shapes was demonstrated as a means to generate average relative organizations (correlations) between the complexes. The presence of these correlated structures was shown through comparisons of the structures, phase behavior, and the immiscibility between materials having the same phase but different shapes. Correlated structures were shown which produce average rotations of 90{degrees} and 180{degrees} between nearest-neighbor molecules. A crystal structure of one compound confirmed that a similar superstructure was exhibited in the solid state. In addition, it was found that the correlated structures exhibit relatively short (3.29 {angstrom}) correlations between the mesogens, thereby allowing for strong intermolecular interactions. The ability to control the orientation and relative position of transition metal centers in liquid crystals has applications in the design of new liquid-crystalline materials with useful magnetic and electronic properties. 32 refs., 8 figs., 8 tabs.

  20. A highly sensitive non-enzymatic glucose sensor based on bimetallic Cu-Ag superstructures.

    PubMed

    Li, Hua; Guo, Chun-Yan; Xu, Cai-Ling

    2015-01-15

    Bimetallic Cu-Ag superstructures were successfully fabricated for the first time by using the natural leaves as reducing agent through a facile one-step hydrothermal process. Morphology, structure and composition of the Cu-Ag superstructures were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES), respectively. The results reveal that the Cu-Ag superstructure is bimetallic nanocomposite constructed by nanoparticles with low Ag content and shows a rough surface and porous flexural algae-like microstructure. By using a three-dimensional nickel foam as the scaffold, a novel non-enzymatic glucose sensor based on Cu-Ag nanocomposites has been fabricated and applied to non-enzymatic glucose detection. The as-prepared Cu-Ag nanocomposites based glucose sensor displays distinctly enhanced electrocatalytic activity compared to those obtained with pure Cu nanomaterials prepared with a similar procedure, revealing a synergistic effect of the matrix Cu and the doped Ag. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy indicate that the Cu-Ag superstructures based glucose sensor displays a fascinating sensitivity up to 7745.7 μA mM(-1) cm(-2), outstanding detection limit of 0.08 μM and fast amperometric response (<2 s) for glucose detection. Furthermore, the sensor also exhibits significant selectivity, excellent stability and reproducibility, as well as attractive feasibility for real sample analysis. Because of its excellent electrochemical performance, low cost and easy preparation, this novel electrode material is a promising candidate in the development of non-enzymatic glucose sensor. PMID:25113052

  1. Bimetallic complexes of spiro-azacrown ligands as catalysts of phosphoester and phosphoric anhydride cleavage.

    PubMed

    Wang, Qi; Mikkola, Satu; Lönnberg, Harri

    2004-09-01

    The ability of bimetallic homo- and heteronuclear complexes of two spiro-linked ligands, viz. a biazacrown (i.e., 2,6,10,14,18,22-hexaazaspiro[11.11]tricosane (1)) and an azacrown-crown ether (i.e., 14,17,20,23,26-pentaoxa-2,6,10-triaza-spiro[11.15]heptacosane (2)), to promote the cleavage of the phosphoester linkage of dinucleoside 3',5'-phosphates and the phosphoric anhydride bridge of dinucleoside 5',5'-triphosphates was studied. In both reactions, the bimetallic homonuclear Cu2+ and Zn2+ complexes were better catalysts than their monometallic counterparts. The acceleration was two- to five-fold with the phosphoester cleavage and 3- to 20-fold with the phosphoric anhydride cleavage. Interestingly, the most-efficient catalyst of the phosphoester cleavage was the heterodinuclear Ni2+,Zn2+ complex of 1, the catalytic activity of which was up to 5- and 100-fold that of the homodinuclear Zn2+ and Ni2+ complexes, respectively. Moreover, this cooperative acceleration was observed to depend on the identity of the 5'-linked nucleoside: 3',5'-UpU and 3',5'-ApU were cleaved much faster than 3',5'-UpA, and no cooperative acceleration was observed with 3',5'-ApA. The reaction was second-order in hydroxide ion concentration, suggesting that a double deprotonation took place on going from the initial to the transition state. Evidently, in addition to deprotonation of the attacking 2'-OH group, N(3)H of the 5'-linked uridine was displaced by one of the metal ions of the cleaving agent. With the phosphoric anhydride cleavage, no similar cooperativity of two different metal ions was observed, but the greatest rate-acceleration was achieved with the homodinuclear Cu2+ complexes.

  2. The synthesis of open-shell, bimetallic Mn/Fe trinuclear clusters

    PubMed Central

    Powers, Tamara M.; Gu, Nina; Fout, Alison R.; Baldwin, Anne M.; Sánchez, Raúl Hernández; Alfonso, Denise M.; Chen, Yu-Sheng; Zheng, Shao-Liang

    2013-01-01

    Concomitant deprotonation and metallation of hexadentate ligand platform tbsLH6 (tbsLH6 = 1,3,5-C6H9(NHC6H4-o-NHSiMe2 tBu)3) with divalent transition metal starting materials Fe2(Mes)4 (Mes = mesityl) or Mn3(Mes)6 in the presence of tetrahydrofuran (THF) resulted in isolation of homotrinuclear complexes (tbsL)Fe3(THF) and (tbsL)Mn3(THF) respectively. In the absence of coordinating solvent (THF) the deprotonation and metallation exclusively afforded dinuclear complexes of the type (tbsLH2)M2 (M = Fe or Mn). The resulting dinuclear species were utilized as synthons to prepare bimetallic trinuclear clusters. Treatment of (tbsLH2)Fe2 complex with divalent Mn source (Mn2(N(SiMe3)2)4) afforded the bimetallic complex (tbsL)Fe2Mn(THF) which established the ability of hexamine ligand tbsLH6 to support mixed metal clusters. The substitutional homogeneity of (tbsL)Fe2Mn(THF) was determined by 1H NMR, 57Fe Mössbauer, and X-ray fluorescence. Anomalous scattering measurements were critical for the unambiguous assignment of the trinuclear core composition. Heating a solution of (tbsLH2)Mn2 with a stoichiometric amount of Fe2(Mes)4 (0.5 mol equiv) affords a mixture of both (tbsL)Mn2Fe(THF) and (tbsL)Fe2Mn(THF) as a result of the thermodynamic preference for heavier metal substitution within the hexa-anilido ligand framework. These results demonstrate for the first time the assembly of mixed metal cluster synthesis in an unbiased ligand platform. PMID:23984911

  3. Novel platinum-palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities.

    PubMed

    Ghosh, Sougata; Nitnavare, Rahul; Dewle, Ankush; Tomar, Geetanjali B; Chippalkatti, Rohan; More, Piyush; Kitture, Rohini; Kale, Sangeeta; Bellare, Jayesh; Chopade, Balu A

    2015-01-01

    Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum-palladium bimetallic nanoparticles (Pt-PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2-5 nm, while PdNPs and Pt-PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88% ± 1.73% elemental Pt and 68.96% ± 1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm(-1), attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm(-1), associated with C-H stretching, N-H bending in primary amines, N-O stretching in nitro group, and C-C stretch, respectively. Anticancer activity against HeLa cells showed that Pt-PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt-PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals.

  4. Bimetallic complexes of spiro-azacrown ligands as catalysts of phosphoester and phosphoric anhydride cleavage.

    PubMed

    Wang, Qi; Mikkola, Satu; Lönnberg, Harri

    2004-09-01

    The ability of bimetallic homo- and heteronuclear complexes of two spiro-linked ligands, viz. a biazacrown (i.e., 2,6,10,14,18,22-hexaazaspiro[11.11]tricosane (1)) and an azacrown-crown ether (i.e., 14,17,20,23,26-pentaoxa-2,6,10-triaza-spiro[11.15]heptacosane (2)), to promote the cleavage of the phosphoester linkage of dinucleoside 3',5'-phosphates and the phosphoric anhydride bridge of dinucleoside 5',5'-triphosphates was studied. In both reactions, the bimetallic homonuclear Cu2+ and Zn2+ complexes were better catalysts than their monometallic counterparts. The acceleration was two- to five-fold with the phosphoester cleavage and 3- to 20-fold with the phosphoric anhydride cleavage. Interestingly, the most-efficient catalyst of the phosphoester cleavage was the heterodinuclear Ni2+,Zn2+ complex of 1, the catalytic activity of which was up to 5- and 100-fold that of the homodinuclear Zn2+ and Ni2+ complexes, respectively. Moreover, this cooperative acceleration was observed to depend on the identity of the 5'-linked nucleoside: 3',5'-UpU and 3',5'-ApU were cleaved much faster than 3',5'-UpA, and no cooperative acceleration was observed with 3',5'-ApA. The reaction was second-order in hydroxide ion concentration, suggesting that a double deprotonation took place on going from the initial to the transition state. Evidently, in addition to deprotonation of the attacking 2'-OH group, N(3)H of the 5'-linked uridine was displaced by one of the metal ions of the cleaving agent. With the phosphoric anhydride cleavage, no similar cooperativity of two different metal ions was observed, but the greatest rate-acceleration was achieved with the homodinuclear Cu2+ complexes. PMID:17191909

  5. Novel platinum-palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities.

    PubMed

    Ghosh, Sougata; Nitnavare, Rahul; Dewle, Ankush; Tomar, Geetanjali B; Chippalkatti, Rohan; More, Piyush; Kitture, Rohini; Kale, Sangeeta; Bellare, Jayesh; Chopade, Balu A

    2015-01-01

    Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum-palladium bimetallic nanoparticles (Pt-PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2-5 nm, while PdNPs and Pt-PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88% ± 1.73% elemental Pt and 68.96% ± 1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm(-1), attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm(-1), associated with C-H stretching, N-H bending in primary amines, N-O stretching in nitro group, and C-C stretch, respectively. Anticancer activity against HeLa cells showed that Pt-PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt-PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals. PMID:26719690

  6. Low-temperature aqueous-phase reforming of ethanol on bimetallic PdZn catalysts

    SciTech Connect

    Xiong, Haifeng; DelaRiva, Andrew; Wang, Yong; Dayte, Abhaya

    2015-01-01

    Bimetallic PdZn catalysts supported on carbon black (CB) and carbon nanotubes (CNTs) were found to be selective for CO-free H-2 production from ethanol at low temperature (250 degrees C). On Pd, the H-2 yield was low (similar to 0.3 mol H-2/mol ethanol reacted) and the CH4/CO2 ratio was high (similar to 1.7). Addition of Zn to Pd formed the intermetallic PdZn beta phase (atomic ratio of Zn to Pd is 1) with increased H-2 yield (similar to 1.9 mol H-2/mol ethanol reacted) and CH4/CO2 ratio of <1. The higher H-2 yield and low CH4 formation was related to the improved dehydrogenation activity of the L1(0) PdZn beta phase. The TOF increased with particle size and the CNTs provided the most active and selective catalysts, which may be ascribed to pore-confinement effects. Furthermore, no significant changes in either the supports or the PdZn beta particles was found after aqueous-phase reforming (APR) indicating that the metal nanoparticles and the carbon support are hydrothermally stable in the aqueous phase at elevated temperatures and pressures (>200 degrees C, 65 bar). No CO was detected for all the catalysts performed in aqueous-phase reaction, indicating that both monometallic Pd and bimetallic PdZn catalysts have high water-gas shift activity during APR. However, the yield of H-2 is considerably lower than the theoretical value of 6 H-2 per mole ethanol which is due to the presence of oxygenated products and methane on the PdZn catalysts.

  7. Novel platinum–palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities

    PubMed Central

    Ghosh, Sougata; Nitnavare, Rahul; Dewle, Ankush; Tomar, Geetanjali B; Chippalkatti, Rohan; More, Piyush; Kitture, Rohini; Kale, Sangeeta; Bellare, Jayesh; Chopade, Balu A

    2015-01-01

    Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum–palladium bimetallic nanoparticles (Pt–PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2–5 nm, while PdNPs and Pt–PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88%±1.73% elemental Pt and 68.96%±1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm−1, attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm−1, associated with C–H stretching, N–H bending in primary amines, N–O stretching in nitro group, and C–C stretch, respectively. Anticancer activity against HeLa cells showed that Pt–PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt–PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals. PMID:26719690

  8. Bimetallic nickel-iron nanoparticles for groundwater decontamination: effect of groundwater constituents on surface deactivation.

    PubMed

    Han, Yanlai; Yan, Weile

    2014-12-01

    The incorporation of catalytic metals on iron nanoparticles to form bimetallic nanoparticles (BNPs) generates a class of highly reactive materials for degrading chlorinated hydrocarbons (e.g., trichloroethylene, TCE) in groundwater. Successful implementation of BNPs to groundwater decontamination relies critically on the stability of surface reactive sites of BNPs in groundwater matrices. This study investigated the effect of common groundwater solutes on TCE reduction with Ni-Fe (with Ni at 2 wt.%) bimetallic nanoparticles (herein denoted as Ni-Fe BNPs). Batch experiments involving pre-exposing the nanoparticles to various groundwater solutions for 24 h followed by reactions with TCE solutions were conducted. The results suggest that the deactivation behavior of Ni-Fe BNPs differs significantly from that of the well-studied Pd-Fe BNPs. Specifically, Ni-Fe BNPs were chemically stable in pure water. Mild reduction in TCE reaction rates were observed for Ni-Fe BNPs pre-exposed to chloride (Cl(-)), bicarbonate (HCO3(-)), sulfite (SO3(2-)) and humic acid solutions. Nitrate (NO3(-)), sulfate (SO4(2-)) and phosphate (HPO4(2-)) may cause moderate to severe deactivation at elevated concentrations (>1 mM). Product analysis and surface chemistry investigations using high-resolution X-ray photoelectron spectroscopy (HR-XPS) reveal that NO3(-) decreased particle reactivity mainly due to progressive formation of passivating oxides, whereas SO4(2-) and phosphate elicited rapid deactivation as a result of specific poisoning of the surface nickel sites. At similar levels, phosphate is the most potent deactivation agent among the solutes examined in this study. While our findings point out the desirable quality of Ni-Fe nanoparticles, particularly their greater electrochemical stability compared to Pd-Fe BNPs, its susceptibility to chemical poisoning at high levels of complexing ligands is also noted. Groundwater chemistry is therefore an important factor to consider when

  9. [Preparation bimetallic heterogeneous Fenton-like catalyst as sepiolite supported and its surface chemical characterization].

    PubMed

    Su, Cheng-yuan; Li, Wei-guang; Liu, Xing-zhe; Wang, Kai-yao; Wang, Yong

    2013-09-01

    The reactive brilliant blue was chosen as the probe pollutant. Fe(NO3)3 concentration, MnSO4 concentration, urea concentration, water bath temperature, calcined temperature and time were as influencing factors, the process parameters of homogeneous precipitation method was optimized for the preparation of bimetallic heterogeneous Fenton-like catalyst as modified sepiolite supported. At the same time, surface chemical characteristics of catalyst were analyzed by SEM, FTIR and XRD. Results showed that: with increasing iron ion concentrations, the active ingredient of the catalyst increased. Adding small amount of manganese ion could inhibit the growth of Fe2O3 diameter and increase the activity of the catalyst. Urea concentration was increased, so that the higher the urea concentration, the higher rate of formation of crystal gains, was conducive to generate small and uniform particles. The optimal conditions were found for preparing bimetallic heterogeneous Fenton-like catalyst by Box-Behnken experiment, which were as follows: concentration of Fe(NO3)3, MnSO4 and urea were 0.18 mol x L(-1), 0.05 mol x L(-1) and 1.0 mol x L(-1), respectively. The dosage of the modified sepiolite was 40 g x L(-1) and water bath temperature was 100 degrees C. Additionally, the catalyst was calcined at 370 degrees C for 3 h. The SEM showed that the sepiolite was an a-type sepiolite, which could be used as a well catalyst support. The infrared spectrum presented the bend vibrations of the Fe-O stretch vibration. The XRD patterns of the catalysts showed the characteristic diffraction peaks of alpha-Fe2O3, and gamma-Fe2O3.

  10. Nanostructured materials in electroanalysis of pharmaceuticals.

    PubMed

    Rahi, A; Karimian, K; Heli, H

    2016-03-15

    Basic strategies and recent developments for the enhancement of the sensory performance of nanostructures in the electroanalysis of pharmaceuticals are reviewed. A discussion of the properties of nanostructures and their application as modified electrodes for drug assays is presented. The electrocatalytic effect of nanostructured materials and their application in determining low levels of drugs in pharmaceutical forms and biofluids are discussed.

  11. Method of fabrication of anchored nanostructure materials

    DOEpatents

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2013-11-26

    Methods for fabricating anchored nanostructure materials are described. The methods include heating a nano-catalyst under a protective atmosphere to a temperature ranging from about 450.degree. C. to about 1500.degree. C. and contacting the heated nano-catalysts with an organic vapor to affix carbon nanostructures to the nano-catalysts and form the anchored nanostructure material.

  12. Interfacing nanostructures to biological cells

    DOEpatents

    Chen, Xing; Bertozzi, Carolyn R.; Zettl, Alexander K.

    2012-09-04

    Disclosed herein are methods and materials by which nanostructures such as carbon nanotubes, nanorods, etc. are bound to lectins and/or polysaccharides and prepared for administration to cells. Also disclosed are complexes comprising glycosylated nanostructures, which bind selectively to cells expressing glycosylated surface molecules recognized by the lectin. Exemplified is a complex comprising a carbon nanotube functionalized with a lipid-like alkane, linked to a polymer bearing repeated .alpha.-N-acetylgalactosamine sugar groups. This complex is shown to selectively adhere to the surface of living cells, without toxicity. In the exemplified embodiment, adherence is mediated by a multivalent lectin, which binds both to the cells and the .alpha.-N-acetylgalactosamine groups on the nanostructure.

  13. PREFACE: Self-organized nanostructures

    NASA Astrophysics Data System (ADS)

    Rousset, Sylvie; Ortega, Enrique

    2006-04-01

    In order to fabricate ordered arrays of nanostructures, two different strategies might be considered. The `top-down' approach consists of pushing the limit of lithography techniques down to the nanometre scale. However, beyond 10 nm lithography techniques will inevitably face major intrinsic limitations. An alternative method for elaborating ultimate-size nanostructures is based on the reverse `bottom-up' approach, i.e. building up nanostructures (and eventually assemble them to form functional circuits) from individual atoms or molecules. Scanning probe microscopies, including scanning tunnelling microscopy (STM) invented in 1982, have made it possible to create (and visualize) individual structures atom by atom. However, such individual atomic manipulation is not suitable for industrial applications. Self-assembly or self-organization of nanostructures on solid surfaces is a bottom-up approach that allows one to fabricate and assemble nanostructure arrays in a one-step process. For applications, such as high density magnetic storage, self-assembly appears to be the simplest alternative to lithography for massive, parallel fabrication of nanostructure arrays with regular sizes and spacings. These are also necessary for investigating the physical properties of individual nanostructures by means of averaging techniques, i.e. all those using light or particle beams. The state-of-the-art and the current developments in the field of self-organization and physical properties of assembled nanostructures are reviewed in this issue of Journal of Physics: Condensed Matter. The papers have been selected from among the invited and oral presentations of the recent summer workshop held in Cargese (Corsica, France, 17-23 July 2005). All authors are world-renowned in the field. The workshop has been funded by the Marie Curie Actions: Marie Curie Conferences and Training Courses series named `NanosciencesTech' supported by the VI Framework Programme of the European Community, by

  14. Nanostructure Neutron Converter Layer Development

    NASA Technical Reports Server (NTRS)

    Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Kang, Jin Ho (Inventor); Lowther, Sharon E. (Inventor); Thibeault, Sheila A. (Inventor); Bryant, Robert G. (Inventor)

    2016-01-01

    Methods for making a neutron converter layer are provided. The various embodiment methods enable the formation of a single layer neutron converter material. The single layer neutron converter material formed according to the various embodiments may have a high neutron absorption cross section, tailored resistivity providing a good electric field penetration with submicron particles, and a high secondary electron emission coefficient. In an embodiment method a neutron converter layer may be formed by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In another embodiment method a neutron converter layer may be formed by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In a further embodiment method a neutron converter layer may be formed by in-situ metalized aerogel nanostructure development.

  15. Properties of Ferroelectric Nanostructures

    NASA Astrophysics Data System (ADS)

    Ponomareva, Inna

    2008-03-01

    Ferroelectric nanostructures (FENs) such as thin films, nanowires and nanodots are receiving a lot of attention due to their potential for technological applications and to the rich variety of underlying physics. Interestingly, properties of FENs can substantially deviate from their bulk counterpart due to their sensitivity to many factors. Examples of such factors are the electrical boundary conditions (associated with the full, partial or non-existent screening of polarization-induced surface charges) and mechanical boundary conditions (arising from the lattice mismatch between the FEN and its substrate). Here, we developed and used computational schemes to predict many properties in various FENs, as well as, to provide atomistic insight to their complex phenomena. In particular, we will show the striking following features and reveal their origins: *The interplay between electrical boundary conditions, mechanical boundary conditions and growth direction results in the appearance of novel dipole patterns and new low-symmetry phases possessing superior dielectric properties in ferroelectric dots, wires and films [1,2]. *FENs can exhibit dielectric anomalies, such as a negative dielectric susceptibility [3]. *Nanobubbles can form in ferroelectric films under an external electric field [4]. *An homogeneous electric field can be used to control the chirality of vortex structures in asymmetric ferroelectric dots, via the creation of original intermediate states [5]. [1] I. Ponomareva et al., Phys. Rev. B 72, 214118 (2005). [2] I. Ponomareva and L. Bellaiche, Phys. Rev. B 74, 064102 (2006). [3] I. Ponomareva et al., to be published in Phys. Rev. Lett. (2007). [4] B.-K. Lai et al., Phys. Rev. Lett. 96, 137602 (2006). [5] S. Prosandeev et al., submitted (2007). These works have been done in collaboration with L. Bellaiche, I. Kornev, B.-K. Lai, I.I. Naumov, R. Resta and S. Prosandeev. Some computations were made possible thanks to the MRI Grants 0421099 and 0722625 from

  16. Nanostructured Substrates for Optical Sensing

    PubMed Central

    Kemling, Jonathan W.; Qavi, Abraham J.; Bailey, Ryan C.

    2011-01-01

    Sensors that change color have the advantages of versatility, ease of use, high sensitivity, and low cost. The recent development of optically based chemical sensing platforms has increasingly employed substrates manufactured with advanced processing or fabrication techniques to provide precise control over shape and morphology of the sensor micro- and nano-structure. New sensors have resulted with improved capabilities for a number of sensing applications, including the detection of biomolecules and environmental monitoring. This perspective focuses on recent optical sensor devices that utilize nanostructured substrates. PMID:22174955

  17. Vortex ice in nanostructured superconductors

    SciTech Connect

    Reichhardt, Charles; Reichhardt, Cynthia J; Libal, Andras J

    2008-01-01

    We demonstrate using numerical simulations of nanostructured superconductors that it is possible to realize vortex ice states that are analogous to square and kagome ice. The system can be brought into a state that obeys either global or local ice rules by applying an external current according to an annealing protocol. We explore the breakdown of the ice rules due to disorder in the nanostructure array and show that in square ice, topological defects appear along grain boundaries, while in kagome ice, individual defects appear. We argue that the vortex system offers significant advantages over other artificial ice systems.

  18. Breakdown of the Hume-Rothery rules in sub-nanometer-sized Ta-containing bimetallic small clusters.

    PubMed

    Miyajima, Ken; Fukushima, Naoya; Himeno, Hidenori; Yamada, Akira; Mafuné, Fumitaka

    2009-12-01

    The Hume-Rothery rules are empirical rules to predict the solid solubility of metals. We examined whether the rules hold for sub-nanometer-sized small particles. We prepared bimetallic cluster ions in the gas phase by a double laser ablation technique. Taking advantage of the magic compositions of the bimetallic cluster ions relating to the distinguished stabilities, the coalescence or the segregation of Ta and another element in the sub-nanometer-sized clusters was discussed. It was found that W, Nb, and Mo readily coalesce with Ta, while Ag, Al, Au, Co, Cu, Fe, Hf, Ni, Pt, Ti, and V are segregated from Ta. On the basis of these results, we concluded that the Hume-Rothery rules do not hold for sub-nanometer-sized particles. PMID:19894706

  19. Synthesis of bimetallic Pt-Pd core-shell nanocrystals and their high electrocatalytic activity modulated by Pd shell thickness

    NASA Astrophysics Data System (ADS)

    Li, Yujing; Wang, Zhi Wei; Chiu, Chin-Yi; Ruan, Lingyan; Yang, Wenbing; Yang, Yang; Palmer, Richard E.; Huang, Yu

    2012-01-01

    Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more resistant to the CO poisoning than Pt NCs and Pt black. It is also demonstrated that the bimetallic Pt-Pd core-shell NCs can enhance the current density of the methanol oxidation reaction, lowering the over-potential by 35 mV with respect to the Pt core NCs. Further investigation reveals that the Pd/Pt ratio of 1/3, which corresponds to nearly monolayer Pd deposition on Pt core NCs, gives the highest oxidation current density and lowest over-potential. This study shows for the first time the systematic investigation of effects of Pd atomic shells on Pt-Pd bimetallic nanocatalysts, providing valuable guidelines for designing high-performance catalysts for fuel cell applications.Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more

  20. Synergistic geometric and electronic effects for electrochemical reduction of carbon dioxide using gold-copper bimetallic nanoparticles.

    PubMed

    Kim, Dohyung; Resasco, Joaquin; Yu, Yi; Asiri, Abdullah Mohamed; Yang, Peidong

    2014-09-11

    Highly efficient and selective electrochemical reduction of carbon dioxide represents one of the biggest scientific challenges in artificial photosynthesis, where carbon dioxide and water are converted into chemical fuels from solar energy. However, our fundamental understanding of the reaction is still limited and we do not have the capability to design an outstanding catalyst with great activity and selectivity a priori. Here we assemble uniform gold-copper bimetallic nanoparticles with different compositions into ordered monolayers, which serve as a well-defined platform to understand their fundamental catalytic activity in carbon dioxide reduction. We find that two important factors related to intermediate binding, the electronic effect and the geometric effect, dictate the activity of gold-copper bimetallic nanoparticles. These nanoparticle monolayers also show great mass activities, outperforming conventional carbon dioxide reduction catalysts. The insights gained through this study may serve as a foundation for designing better carbon dioxide electrochemical reduction catalysts.

  1. Breakdown of the Hume-Rothery rules in sub-nanometer-sized Ta-containing bimetallic small clusters.

    PubMed

    Miyajima, Ken; Fukushima, Naoya; Himeno, Hidenori; Yamada, Akira; Mafuné, Fumitaka

    2009-12-01

    The Hume-Rothery rules are empirical rules to predict the solid solubility of metals. We examined whether the rules hold for sub-nanometer-sized small particles. We prepared bimetallic cluster ions in the gas phase by a double laser ablation technique. Taking advantage of the magic compositions of the bimetallic cluster ions relating to the distinguished stabilities, the coalescence or the segregation of Ta and another element in the sub-nanometer-sized clusters was discussed. It was found that W, Nb, and Mo readily coalesce with Ta, while Ag, Al, Au, Co, Cu, Fe, Hf, Ni, Pt, Ti, and V are segregated from Ta. On the basis of these results, we concluded that the Hume-Rothery rules do not hold for sub-nanometer-sized particles.

  2. Synergistic geometric and electronic effects for electrochemical reduction of carbon dioxide using gold-copper bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Dohyung; Resasco, Joaquin; Yu, Yi; Asiri, Abdullah Mohamed; Yang, Peidong

    2014-09-01

    Highly efficient and selective electrochemical reduction of carbon dioxide represents one of the biggest scientific challenges in artificial photosynthesis, where carbon dioxide and water are converted into chemical fuels from solar energy. However, our fundamental understanding of the reaction is still limited and we do not have the capability to design an outstanding catalyst with great activity and selectivity a priori. Here we assemble uniform gold-copper bimetallic nanoparticles with different compositions into ordered monolayers, which serve as a well-defined platform to understand their fundamental catalytic activity in carbon dioxide reduction. We find that two important factors related to intermediate binding, the electronic effect and the geometric effect, dictate the activity of gold-copper bimetallic nanoparticles. These nanoparticle monolayers also show great mass activities, outperforming conventional carbon dioxide reduction catalysts. The insights gained through this study may serve as a foundation for designing better carbon dioxide electrochemical reduction catalysts.

  3. Synergistic geometric and electronic effects for electrochemical reduction of carbon dioxide using gold-copper bimetallic nanoparticles.

    PubMed

    Kim, Dohyung; Resasco, Joaquin; Yu, Yi; Asiri, Abdullah Mohamed; Yang, Peidong

    2014-01-01

    Highly efficient and selective electrochemical reduction of carbon dioxide represents one of the biggest scientific challenges in artificial photosynthesis, where carbon dioxide and water are converted into chemical fuels from solar energy. However, our fundamental understanding of the reaction is still limited and we do not have the capability to design an outstanding catalyst with great activity and selectivity a priori. Here we assemble uniform gold-copper bimetallic nanoparticles with different compositions into ordered monolayers, which serve as a well-defined platform to understand their fundamental catalytic activity in carbon dioxide reduction. We find that two important factors related to intermediate binding, the electronic effect and the geometric effect, dictate the activity of gold-copper bimetallic nanoparticles. These nanoparticle monolayers also show great mass activities, outperforming conventional carbon dioxide reduction catalysts. The insights gained through this study may serve as a foundation for designing better carbon dioxide electrochemical reduction catalysts. PMID:25208828

  4. One step electrochemical synthesis of bimetallic PdAu supported on nafion–graphene ribbon film for ethanol electrooxidation

    SciTech Connect

    Shendage, Suresh S. Singh, Abilash S.; Nagarkar, Jayashree M.

    2015-10-15

    Highlights: • Electrochemical deposition of bimetallic PdAu NPs. • Highly loaded PdAu NPs are obtained. • Nafion–graphene supported PdAu NPs shows good activity for ethanol electrooxidation. - Abstract: A nafion–graphene ribbon (Nf–GR) supported bimetallic PdAu nanoparticles (PdAu/Nf–GR) catalyst was prepared by electrochemical codeposition of Pd and Au at constant potential. The prepared catalyst was characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The average particle size of PdAu nanoparticles (NPs) determined from XRD was 3.5 nm. The electrocatalytic activity of the PdAu/Nf–GR catalyst was examined by cyclic voltametry. It was observed that the as prepared catalyst showed efficient activity and good stability for ethanol electrooxidation in alkaline medium.

  5. Direct writing of CoFe alloy nanostructures by focused electron beam induced deposition from a heteronuclear precursor

    NASA Astrophysics Data System (ADS)

    Porrati, F.; Pohlit, M.; Müller, J.; Barth, S.; Biegger, F.; Gspan, C.; Plank, H.; Huth, M.

    2015-11-01

    Recently, focused electron beam-induced deposition has been employed to prepare functional magnetic nanostructures with potential in nanomagnetic logic and sensing applications by using homonuclear precursor gases like Fe(CO)5 or Co2(CO)8. Here we show that an extension towards the fabrication of bi-metallic compounds is possible by using a single-source heteronuclear precursor gas. We have grown CoFe alloy magnetic nanostructures from the HFeCo3(CO)12 metal carbonyl precursor. The compositional analysis indicates that the samples contain about 80 at% of metal and 10 at% of carbon and oxygen. Four-probe magnetotransport measurements are carried out on nanowires of various sizes down to a width of 50 nm, for which a room temperature resistivity of 43 μΩcm is found. Micro-Hall magnetometry reveals that 50 nm × 250 nm nanobars of the material are ferromagnetic up to the highest measured temperature of 250 K. Finally, the transmission electron microscopy (TEM) microstructural investigation shows that the deposits consist of a bcc Co-Fe phase mixed with a FeCo2 O4 spinel oxide phase with nanograins of about 5 nm diameter.

  6. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October--December 1992

    SciTech Connect

    Song, Chunshan; Schobert, H.H.

    1993-02-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

  7. The catalytic behavior of precisely synthesized Pt–Pd bimetallic catalysts for use as diesel oxidation catalysts

    DOE PAGES

    Wong, Andrew P.; Kyriakidou, Eleni A.; Toops, Todd J.; Regalbuto, John R.

    2016-04-17

    The demands of stricter diesel engine emission regulations have created challenges for current exhaust systems. With advances in low-temperature internal combustion engines and their operations, advances must also be made in vehicle exhaust catalysts. Most current diesel oxidation catalysts use heavy amounts of precious group metals (PGMs) for hydrocarbon (HC), CO, and NO oxidation. These catalysts are expensive and are most often synthesized with poor bimetallic interaction and dispersion. In this paper, the goal was to study the effect of aging on diesel emission abatement of Pt–Pd bimetallic nanoparticles precisely prepared with different morphologies: well dispersed core–shell vs. well dispersedmore » homogeneously alloyed vs. poorly dispersed, poorly alloyed particles. Alumina and silica supports were studied. Particle morphology and dispersion were analyzed before and after hydrothermal treatments by XRD, EDX, and STEM. Reactivity as a function of aging was measured in simulated diesel engine exhaust. While carefully controlled bimetallic catalyst nanoparticle structure has a profound influence on initial or low temperature catalytic activity, the differences in behavior disappear with higher temperature aging as thermodynamic equilibrium is achieved. The metallic character of Pt-rich alumina-supported catalysts is such that behavior rather closely follows the Pt–Pd metal phase diagram. Nanoparticles disparately composed as well-dispersed core–shell (via seq-SEA), well-dispersed homogeneously alloyed (via co-SEA), and poorly dispersed, poorly alloyed (via co-DI) end up as well alloyed, large particles of almost the same size and activity. With Pd-rich systems, the oxidation of Pd also figures into the equilibrium, such that Pd-rich oxide phases appear in the high temperature forms along with alloyed metal cores. Finally, the small differences in activity after high temperature aging can be attributed to the synthesis methods, sequential SEA and co

  8. Progress toward Light-Harvesting Self-Electrophoretic Motors: Highly Efficient Bimetallic Nanomotors and Micropumps in Halogen Media.

    PubMed

    Wong, Flory; Sen, Ayusman

    2016-07-26

    We have developed a highly efficient, bubble-free autonomous nanomotor based on a nanobattery. Bimetallic silver-platinum nanorods are powered by self-electrophoresis and show speeds much higher than those of other electrophoretic motors at similar fuel concentrations. The fuel (I2) can be regenerated by exposure to ambient light, leading to renewed motion of the motor. This versatile system can also be made into a micropump that transports fluid and particles.

  9. Facile synthesis of Pd-based bimetallic nanocrystals and their application as catalysts for methanol oxidation reaction

    NASA Astrophysics Data System (ADS)

    Xi, Pinxian; Cao, Yang; Yang, Fengchun; Ma, Cai; Chen, Fengjuan; Yu, Sha; Wang, Shuai; Zeng, Zhengzhi; Zhang, Xin

    2013-06-01

    We employed an efficient and facile route to synthesise monodisperse Pd-based bimetallic nanocrystals (MPd: M = Cu, Co and Ni) via a controlled co-reduction of Pd(ii) chloride and M(ii) nitrate at 200-230 °C in the presence of oleylamine (OAm). These monodisperse Pd-based nanocrystals have small dimensions, unique structures and homogeneous morphology, thus exhibit efficient catalytic activities for methanol oxidation in alkaline solution, which is much better than commercial Pd/C with same amount of palladium. The catalytic activities of these nanocrystals followed the order of NiPd/C > CoPd/C > CuPd/C > commercial Pd/C, due to the different synergistic effects. Our results show that these Pd-based bimetallic nanocrystals can be promising as practical catalysts for methanol oxidation reactions and other catalytic reactions in further investigations.We employed an efficient and facile route to synthesise monodisperse Pd-based bimetallic nanocrystals (MPd: M = Cu, Co and Ni) via a controlled co-reduction of Pd(ii) chloride and M(ii) nitrate at 200-230 °C in the presence of oleylamine (OAm). These monodisperse Pd-based nanocrystals have small dimensions, unique structures and homogeneous morphology, thus exhibit efficient catalytic activities for methanol oxidation in alkaline solution, which is much better than commercial Pd/C with same amount of palladium. The catalytic activities of these nanocrystals followed the order of NiPd/C > CoPd/C > CuPd/C > commercial Pd/C, due to the different synergistic effects. Our results show that these Pd-based bimetallic nanocrystals can be promising as practical catalysts for methanol oxidation reactions and other catalytic reactions in further investigations. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00912b

  10. Catalytic dechlorination of 2,4-dichlorophenol by Pd/Fe bimetallic nanoparticles in the presence of humic acid.

    PubMed

    Zhang, Zhen; Shen, Qiaohui; Cissoko, Naman; Wo, Jingjing; Xu, Xinhua

    2010-10-15

    Pd/Fe bimetallic nanoparticles were synthesized for treatment of 2,4-dichlorophenol (2,4-DCP) in the presence of humic acid (HA), in order to understand their applicability for in situ remediation of groundwater. In this case, 2,4-DCP was catalytically dechlorinated to form the final products--phenol (P) via two intermediates, namely o-chlorophenol (o-CP) and p-chlorophenol (p-CP). We demonstrated that the carbon mass balances during the dechlorination were in the range of 82-91%, and other carbons were absorbed on the surface of Pd/Fe bimetallic nanoparticles. Our results suggest the dechlorination reaction of 2,4-DCP by Pd/Fe bimetallic nanoparticles in the presence of HA followed pseudo-first-order kinetics. HA competed for reaction sites on the Pd/Fe bimetallic nanoparticles with 2,4-DCP, and thus reduced the efficiency and rate of the dechlorination of 2,4-DCP. Efficiencies of dechlorination and phenol formations increased significantly as the Pd content increased from 0.10 wt.%, 0.15 wt.% to 0.20 wt.%, the removal percentage of 2,4-DCP increased from 70.4%, 98.4% to 99.4% within 300 min, respectively, the nitrate (NO(3)(-)) content in water also has a significant impact on 2,4-DCP dechlorination efficiency. Our results show that no other intermediates were generated besides Cl(-), o-CP, p-CP and phenol during the catalytic dechlorination of 2,4-DCP.

  11. Controlled placement and orientation of nanostructures

    DOEpatents

    Zettl, Alex K; Yuzvinsky, Thomas D; Fennimore, Adam M

    2014-04-08

    A method for controlled deposition and orientation of molecular sized nanoelectromechanical systems (NEMS) on substrates is disclosed. The method comprised: forming a thin layer of polymer coating on a substrate; exposing a selected portion of the thin layer of polymer to alter a selected portion of the thin layer of polymer; forming a suspension of nanostructures in a solvent, wherein the solvent suspends the nanostructures and activates the nanostructures in the solvent for deposition; and flowing a suspension of nanostructures across the layer of polymer in a flow direction; thereby: depositing a nanostructure in the suspension of nanostructures only to the selected portion of the thin layer of polymer coating on the substrate to form a deposited nanostructure oriented in the flow direction. By selectively employing portions of the method above, complex NEMS may be built of simpler NEMSs components.

  12. Debromination of polybrominated diphenyl ethers by attapulgite-supported Fe/Ni bimetallic nanoparticles: Influencing factors, kinetics and mechanism.

    PubMed

    Liu, Zongtang; Gu, Chenggang; Ye, Mao; Bian, Yongrong; Cheng, Yinwen; Wang, Fang; Yang, Xinglun; Song, Yang; Jiang, Xin

    2015-11-15

    To enhance the removal efficiency of 2,2',4,4'-tetrabromodiphenylether (BDE47) in aqueous solutions, novel attapulgite-supported Fe/Ni bimetallic nanoparticles (A-Fe/Ni), which were characterized by a core-shell nanoparticle structure and with an average diameter of 20-40 nm, were synthesized for use in BDE47 degradation. The presence of attapulgite in bimetallic systems could reduce Fe/Ni nanoparticle aggregation and enhance their reactivity. BDE47 was degraded with a significant improvement in removal efficiency of at least 96% by A-Fe/Ni that played a reductive role in the reaction. The degradation kinetics of BDE47 by A-Fe/Ni complied with pseudo-first-order characteristics. To better understand the removal mechanism, detailed analyses were performed for several influential parameters. The improved dosage of A-Fe/Ni was found to be beneficial, and higher values of initial concentration, pH, and methanol/water ratio hindered the degradation rate, which, for example, decreased significantly in mixtures with a methanol proportion higher than 50%. The identification of BDE47 degradation products revealed a stepwise debromination from n-bromo-DE to (n-1)-bromo-DE as a possible pathway, wherein the para-Br was more easily eliminated than ortho-Br. Our findings provide insight into the removal mechanism and evidence for polybrominated diphenyl ether debromination by clay-Fe/Ni bimetallic nanoparticles. PMID:26094061

  13. Atomic structure and thermal stability of Pt-Fe bimetallic nanoparticles: from alloy to core/shell architectures.

    PubMed

    Huang, Rao; Wen, Yu-Hua; Shao, Gui-Fang; Sun, Shi-Gang

    2016-06-22

    Bimetallic nanoparticles comprising noble metal and non-noble metal have attracted intense interest over the past few decades due to their low cost and significantly enhanced catalytic performances. In this article, we have explored the atomic structure and thermal stability of Pt-Fe alloy and core-shell nanoparticles by molecular dynamics simulations. In Fe-core/Pt-shell nanoparticles, Fe with three different structures, i.e., body-centered cubic (bcc), face-centered cubic (fcc), and amorphous phases, has been considered. Our results show that Pt-Fe alloy is the most stable configuration among the four types of bimetallic nanoparticles. It has been discovered that the amorphous Fe cannot stably exist in the core and preferentially transforms into the fcc phase. The phase transition from bcc to hexagonal close packed (hcp) has also been observed in bcc-Fe-core/Pt-shell nanoparticles. In contrast, Fe with the fcc structure is the most preferred as the core component. These findings are helpful for understanding the structure-property relationships of Pt-Fe bimetallic nanoparticles, and are also of significance to the synthesis and application of noble metal based nanoparticle catalysts. PMID:27297782

  14. Mixed-phase Pd-Pt bimetallic alloy on graphene oxide with high activity for electrocatalytic applications

    NASA Astrophysics Data System (ADS)

    Khan, Majid; Yousaf, Ammar Bin; Chen, Mingming; Wei, Chengsha; Wu, Xibo; Huang, Ningdong; Qi, Zeming; Li, Liangbin

    2015-05-01

    Bimetallic PdPt alloy nanoparticles on graphene oxide (GO) have been prepared by a simple and facile chemical route, in which the reduction of metal precursors is carried out using CO as a reductant. Structural and morphological characterizations of GO/PdPt composites are performed using X-ray diffraction, X-ray photoelectron spectroscopy analysis and transmission electron microscopy. It is found that PdPt bimetallic nanoparticles are successfully synthesized and uniformly attached on the graphene sheets. The electrocatalytic and electrochemical properties of GO/PdPt composites including methanol oxidation reaction (MOR), oxygen reduction reaction (ORR) and methanol tolerant oxygen reduction reaction (MTORR) are studied in HClO4 aqueous solution. A significant improvement in the electrocatalytic activities is observed by increasing the atomic ratio of Pt in PdPt bimetallic alloys compared to the freestanding Pd nanoparticles on GO. The prepared GO/PdPt composites with an (Pd:Pt) atomic ratio of 40:60 exhibits higher methanol oxidation activity, higher specific ORR activity and better tolerance to CO poisoning. The results can be attributed to the collective effects of the PdPt nanoparticles and the enhanced electron transfer of graphene.

  15. Atomic structure and thermal stability of Pt-Fe bimetallic nanoparticles: from alloy to core/shell architectures.

    PubMed

    Huang, Rao; Wen, Yu-Hua; Shao, Gui-Fang; Sun, Shi-Gang

    2016-06-22

    Bimetallic nanoparticles comprising noble metal and non-noble metal have attracted intense interest over the past few decades due to their low cost and significantly enhanced catalytic performances. In this article, we have explored the atomic structure and thermal stability of Pt-Fe alloy and core-shell nanoparticles by molecular dynamics simulations. In Fe-core/Pt-shell nanoparticles, Fe with three different structures, i.e., body-centered cubic (bcc), face-centered cubic (fcc), and amorphous phases, has been considered. Our results show that Pt-Fe alloy is the most stable configuration among the four types of bimetallic nanoparticles. It has been discovered that the amorphous Fe cannot stably exist in the core and preferentially transforms into the fcc phase. The phase transition from bcc to hexagonal close packed (hcp) has also been observed in bcc-Fe-core/Pt-shell nanoparticles. In contrast, Fe with the fcc structure is the most preferred as the core component. These findings are helpful for understanding the structure-property relationships of Pt-Fe bimetallic nanoparticles, and are also of significance to the synthesis and application of noble metal based nanoparticle catalysts.

  16. Heterogenized Bimetallic Pd-Pt-Fe3O4 Nanoflakes as Extremely Robust, Magnetically Recyclable Catalysts for Chemoselective Nitroarene Reduction.

    PubMed

    Byun, Sangmoon; Song, Yeami; Kim, B Moon

    2016-06-15

    A very simple synthesis of bimetallic Pd-Pt-Fe3O4 nanoflake-shaped alloy nanoparticles (NPs) for cascade catalytic reactions such as dehydrogenation of ammonia-borane (AB) followed by the reduction of nitro compounds (R-NO2) to anilines or alkylamines (R-NH2) in methanol at ambient temperature is described. The Pd-Pt-Fe3O4 NPs were easily prepared via a solution phase hydrothermal method involving the simple one-pot coreduction of potassium tetrachloroplatinate (II) and palladium chloride (II) in polyvinylpyrrolidone with subsequent deposition on commercially available Fe3O4 NPs. The bimetallic Pd-Pt alloy NPs decorated on Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. Various nitroarene derivatives were reduced to anilines with very specific chemoselectivity in the presence of other reducible functional groups. The bimetallic Pd-Pt-Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. The nitro reduction proceeded in 5 min with nearly quantitative conversions and yields. Furthermore, the magnetically recyclable nanocatalysts were readily separated using an external magnet and reused up to 250 times without any loss of catalytic activity. A larger scale (10 mmol) reaction was also successfully performed with >99% yield. This efficient, recyclable Pd-Pt-Fe3O4 NPs system can therefore be repetitively utilized for the reduction of various nitro-containing compounds. PMID:27191706

  17. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, April--June 1993

    SciTech Connect

    Song, Chunshan; Parfitt, D.P.; Schobert, H.H.

    1993-08-01

    The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular precursors, that can be used in low concentrations (bimetallic dispersed catalysts for liquefaction of a Montana subbituminous coal (DECS-9) at the loading level of 0.5 wt% Mo on dmmf coal. It was found that the structure of the precursors, in particular the ligands to the metal species, affect the activity of the resulting catalyst significantly. Among the M-M` type precursors tested, Mo-Co thiocubane, Mo{sub 2}Co{sub 2}S{sub 4}(Cp){sub 2}(CO){sub 2} [Cp = cyclopentadiene], designated as MoCo-TC2, produced in-situ the best catalyst The performance of the Mo-Co bimetallic catalyst was further enhanced by using temperature programmed (TPL) conditions consisting of a low temperature soaking at 200{degrees}C, programmed heat-up to 400 or 425{degrees}C followed by a 30 minutes hold. The pro ed heat-up serves as an in-situ activation of catalyst and coal pretreatment, which contributes to more effective hydrogenation of reactive fragments at high temperature.

  18. The use of mechanical alloying for the preparation of palladized magnesium bimetallic particles for the remediation of PCBs.

    PubMed

    Coutts, Janelle L; Devor, Robert W; Aitken, Brian; Hampton, Michael D; Quinn, Jacqueline W; Clausen, Christian A; Geiger, Cherie L

    2011-09-15

    The kinetic rate of dechlorination of a polychlorinated biphenyl (PCB-151) by mechanically alloyed Mg/Pd was studied for optimization of the bimetallic system. Bimetal production was first carried out in a small-scale environment using a SPEX 8000M high-energy ball mill with 4-μm-magnesium and palladium impregnated on graphite, with optimized parameters including milling time and Pd-loading. A 5.57-g sample of bimetal containing 0.1257% Pd and ball milled for 3 min resulted in a degradation rate of 0.00176 min(-1)g(-1) catalyst as the most reactive bimetal. The process was then scaled-up, using a Red Devil 5400 Twin-Arm Paint Shaker, fitted with custom plates to hold milling canisters. Optimization parameters tested included milling time, number of ball bearings used, Pd-loading, and total bimetal mass milled. An 85-g sample of bimetal containing 0.1059% Pd and ball-milled for 23 min with 16 ball bearings yielded the most reactive bimetal with a degradation rate of 0.00122 min(-1)g(-1) catalyst. Further testing showed adsorption did not hinder extraction efficiency and that dechlorination products were only seen when using the bimetallic system, as opposed to any of its single components. The bimetallic system was also tested for its ability to degrade a second PCB congener, PCB-45, and a PCB mixture (Arochlor 1254); both contaminants were seen to degrade successfully. PMID:21807459

  19. Computer Code for Nanostructure Simulation

    NASA Technical Reports Server (NTRS)

    Filikhin, Igor; Vlahovic, Branislav

    2009-01-01

    Due to their small size, nanostructures can have stress and thermal gradients that are larger than any macroscopic analogue. These gradients can lead to specific regions that are susceptible to failure via processes such as plastic deformation by dislocation emission, chemical debonding, and interfacial alloying. A program has been developed that rigorously simulates and predicts optoelectronic properties of nanostructures of virtually any geometrical complexity and material composition. It can be used in simulations of energy level structure, wave functions, density of states of spatially configured phonon-coupled electrons, excitons in quantum dots, quantum rings, quantum ring complexes, and more. The code can be used to calculate stress distributions and thermal transport properties for a variety of nanostructures and interfaces, transport and scattering at nanoscale interfaces and surfaces under various stress states, and alloy compositional gradients. The code allows users to perform modeling of charge transport processes through quantum-dot (QD) arrays as functions of inter-dot distance, array order versus disorder, QD orientation, shape, size, and chemical composition for applications in photovoltaics and physical properties of QD-based biochemical sensors. The code can be used to study the hot exciton formation/relation dynamics in arrays of QDs of different shapes and sizes at different temperatures. It also can be used to understand the relation among the deposition parameters and inherent stresses, strain deformation, heat flow, and failure of nanostructures.

  20. Advanced nanostructured materials for energy storage and conversion

    NASA Astrophysics Data System (ADS)

    Hutchings, Gregory S.

    Due to a global effort to reduce greenhouse gas emissions and to utilize renewable sources of energy, much effort has been directed towards creating new alternatives to fossil fuels. Identifying novel materials for energy storage and conversion can enable radical changes to the current fuel production infrastructure and energy utilization. The use of engineered nanostructured materials in these systems unlocks unique catalytic activity in practical configurations. In this work, research efforts have been focused on the development of nanostructured materials to address the need for both better energy conversion and storage, with applications toward Li-O2 battery electrocatalysts, electrocatalytic generation of H2, conversion of furfural to useful chemicals and fuels, and Li battery anode materials. Highly-active alpha-MnO2 materials were synthesized for use as bifunctional oxygen reduction (ORR) and evolution (OER) catalysts in Li-O2 batteries, and were evaluated under operating conditions with a novel in situ X-ray absorption spectroscopy configuration. Through detailed analysis of local coordination and oxidation states of Mn atoms at key points in the electrochemical cycle, a self-switching behavior affecting the bifunctional activity was identified and found to be critical. In an additional study of materials for lithium batteries, nanostructured TiO2 anode materials doped with first-row transition metals were synthesized and evaluated for improving battery discharge capacity and rate performance, with Ni and Co doping at low levels found to cause the greatest enhancement. In addition to battery technology research, I have also sought to find inexpensive and earth-abundant electrocatalysts to replace state-of-the-art Pt/C in the hydrogen evolution reaction (HER), a systematic computational study of Cu-based bimetallic electrocatalysts was performed. During the screening of dilute surface alloys of Cu mixed with other first-row transition metals, materials with

  1. Fabrication of zein nanostructure

    NASA Astrophysics Data System (ADS)

    Luecha, Jarupat

    resins. The soft lithography technique was mainly used to fabricate micro and nanostructures on zein films. Zein material well-replicated small structures with the smallest size at sub micrometer scale that resulted in interesting photonic properties. The bonding method was also developed for assembling portable zein microfluidic devices with small shape distortion. Zein-zein and zein-glass microfluidic devices demonstrated sufficient strength to facilitate fluid flow in a complex microfluidic design with no leakage. Aside from the fabrication technique development, several potential applications of this environmentally friendly microfluidic device were investigated. The concentration gradient manipulation of Rhodamine B solution in zein-glass microfluidic devices was demonstrated. The diffusion of small molecules such as fluorescent dye into the wall of the zein microfluidic channels was observed. However, with this formulation, zein microfluidic devices were not suitable for cell culture applications. This pioneer study covered a wide spectrum of the implementation of the two nanotechnology approaches to advance zein biomaterial which provided proof of fundamental concepts as well as presenting some limitations. The findings in this study can lead to several innovative research opportunities of advanced zein biomaterials with broad applications. The information from the study of zein nanocomposite structure allows the packaging industry to develop the low cost biodegradable materials with physical property improvement. The information from the study of the zein microfluidic devices allows agro-industry to develop the nanotechnology-enabled microfluidic sensors fabricated entirely from biodegradable polymer for on-site disease or contaminant detection in the fields of food and agriculture.

  2. Synergetic effect of palladium-ruthenium nanostructures for ethanol electrooxidation in alkaline media

    NASA Astrophysics Data System (ADS)

    Monyoncho, Evans A.; Ntais, Spyridon; Soares, Felipo; Woo, Tom K.; Baranova, Elena A.

    2015-08-01

    Palladium-ruthenium nanoparticles supported on carbon PdxRu1-x/C (x = 1, 0.99, 0.95, 0.90, 0.80, 0.50) were prepared using a polyol method for ethanol electrooxidation in alkaline media. The resulting bimetallic catalysts were found to be primarily a mix of Pd metal, Ru oxides and Pd oxides. Their electrocatalytic activity towards ethanol oxidation reaction (EOR) in 1M KOH was studied using cyclic voltammetry and chronoamperometry techniques. Addition of 1-10 at.% Ru to Pd not only lowers the onset oxidation potential for EOR but also produces higher current densities at lower potentials compared to Pd by itself. Thus, Pd90Ru10/C and Pd99Ru1/C provide the current densities of up to six times those of Pd/C at -0.96 V and -0.67 V vs MSE, respectively. The current density at different potentials was found to be dependent on the surface composition of PdxRu1-x/C nanostructures. Pd90Ru10/C catalyst with more surface oxides was found to be active at lower potential compared to Pd99Ru1/C with less surface oxides, which is active at higher potentials. The steady-state current densities of the two best catalysts, Pd90Ru10/C and Pd99Ru1/C, showed minimal surface deactivation from EOR intermediates/products during chronoamperometry.

  3. Nanostructured Ni2 P as a Robust Catalyst for the Hydrolytic Dehydrogenation of Ammonia-Borane.

    PubMed

    Peng, Cheng-Yun; Kang, Lei; Cao, Shuang; Chen, Yong; Lin, Zhe-Shuai; Fu, Wen-Fu

    2015-12-21

    Ammonia-borane (AB) is a promising chemical hydrogen-storage material. However, the development of real-time, efficient, controllable, and safe methods for hydrogen release under mild conditions is a challenge in the large-scale use of hydrogen as a long-term solution for future energy security. A new class of low-cost catalytic system is presented that uses nanostructured Ni2 P as catalyst, which exhibits excellent catalytic activity and high sustainability toward hydrolysis of ammonia-borane with the initial turnover frequency of 40.4 mol(H2)  mol(Ni2P) (-1)  min(-1) under air atmosphere and at ambient temperature. This value is higher than those reported for noble-metal-free catalysts, and the obtained Arrhenius activation energy (Ea =44.6 kJ mol(-1) ) for the hydrolysis reaction is comparable to Ru-based bimetallic catalysts. A clearly mechanistic analysis of the hydrolytic reaction of AB based on experimental results and a density functional theory calculation is presented. PMID:26545954

  4. Center for Fundamental and Applied Research in Nanostructured and Lightweight Materials. Final Technical Summary

    SciTech Connect

    Mullins, Michael; Rogers, Tony; King, Julia; Keith, Jason; Cornilsen, Bahne; Allen, Jeffrey; Gilbert, Ryan; Holles, Joseph

    2010-09-28

    The core projects for this DOE-sponsored Center at Michigan Tech have focused on several of the materials problems identified by the NAS. These include: new electrode materials, enhanced PEM materials, lighter and more effective bipolar plates, and improvement of the carbon used as a current carrier. This project involved fundamental and applied research in the development and testing of lightweight and nanostructured materials to be used in fuel cell applications and for chemical synthesis. The advent of new classes of materials engineered at the nanometer level can produce materials that are lightweight and have unique physical and chemical properties. The grant was used to obtain and improve the equipment infrastructure to support this research and also served to fund seven research projects. These included: 1. Development of lightweight, thermally conductive bipolar plates for improved thermal management in fuel cells; 2. Exploration of pseudomorphic nanoscale overlayer bimetallic catalysts for fuel cells; 3. Development of hybrid inorganic/organic polymer nanocomposites with improved ionic and electronic properties; 4. Development of oriented polymeric materials for membrane applications; 5. Preparation of a graphitic carbon foam current collectors; 6. The development of lightweight carbon electrodes using graphitic carbon foams for battery and fuel cell applications; and 7. Movement of water in fuel cell electrodes.

  5. A Nanostructured Bifunctional platform for Sensing of Glucose Biomarker in Artificial Saliva: Synergy in hybrid Pt/Au surfaces.

    PubMed

    Raymundo-Pereira, Paulo A; Shimizu, Flávio M; Coelho, Dyovani; Piazzeta, Maria H O; Gobbi, Angelo L; Machado, Sergio A S; Oliveira, Osvaldo N

    2016-12-15

    We report on a bimetallic, bifunctional electrode where a platinum (Pt) surface was patterned with nanostructured gold (Au) fingers with different film thicknesses, which was functionalized with glucose oxidase (GOx) to yield a highly sensitive glucose biosensor. This was achieved by using selective adsorption of a self-assembled monolayer (SAM) onto Au fingers, which allowed GOx immobilization only onto the Au-SAM surface. This modified electrode was termed bifunctional because it allowed to simultaneously immobilize the biomolecule (GOx) on gold to catalyze glucose, and detect hydrogen peroxide on Pt sites. Optimized electrocatalytic activity was reached for the architecture Pt/Au-SAM/GOx with 50nm thickness of Au, where synergy between Pt and Au allowed for detection of hydrogen peroxide (H2O2) at a low applied potential (0V vs. Ag/AgCl). Detection was performed for H2O2 in the range between 4.7 and 102.7 nmol L(-1), with detection limit of 3.4×10(-9) mol L(-1) (3.4 nmol L(-1)) and an apparent Michaelis-Menten rate constant of 3.2×10(-6)molL(-1), which is considerably smaller than similar devices with monometallic electrodes. The methodology was validated by measuring glucose in artificial saliva, including in the presence of interferents. The synergy between Pt and Au was confirmed in electrochemical impedance spectroscopy measurements with an increased electron transfer, compared to bare Pt and Au electrodes. The approach for fabricating the reproducible bimetallic Pt/Au electrodes is entirely generic and may be explored for other types of biosensors and biodevices where advantage can be taken of the combination of the two metals. PMID:27399934

  6. A Nanostructured Bifunctional platform for Sensing of Glucose Biomarker in Artificial Saliva: Synergy in hybrid Pt/Au surfaces.

    PubMed

    Raymundo-Pereira, Paulo A; Shimizu, Flávio M; Coelho, Dyovani; Piazzeta, Maria H O; Gobbi, Angelo L; Machado, Sergio A S; Oliveira, Osvaldo N

    2016-12-15

    We report on a bimetallic, bifunctional electrode where a platinum (Pt) surface was patterned with nanostructured gold (Au) fingers with different film thicknesses, which was functionalized with glucose oxidase (GOx) to yield a highly sensitive glucose biosensor. This was achieved by using selective adsorption of a self-assembled monolayer (SAM) onto Au fingers, which allowed GOx immobilization only onto the Au-SAM surface. This modified electrode was termed bifunctional because it allowed to simultaneously immobilize the biomolecule (GOx) on gold to catalyze glucose, and detect hydrogen peroxide on Pt sites. Optimized electrocatalytic activity was reached for the architecture Pt/Au-SAM/GOx with 50nm thickness of Au, where synergy between Pt and Au allowed for detection of hydrogen peroxide (H2O2) at a low applied potential (0V vs. Ag/AgCl). Detection was performed for H2O2 in the range between 4.7 and 102.7 nmol L(-1), with detection limit of 3.4×10(-9) mol L(-1) (3.4 nmol L(-1)) and an apparent Michaelis-Menten rate constant of 3.2×10(-6)molL(-1), which is considerably smaller than similar devices with monometallic electrodes. The methodology was validated by measuring glucose in artificial saliva, including in the presence of interferents. The synergy between Pt and Au was confirmed in electrochemical impedance spectroscopy measurements with an increased electron transfer, compared to bare Pt and Au electrodes. The approach for fabricating the reproducible bimetallic Pt/Au electrodes is entirely generic and may be explored for other types of biosensors and biodevices where advantage can be taken of the combination of the two metals.

  7. Advanced electron microscopy characterization of multimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna Raj

    Research in noble metal nanoparticles has led to exciting progress in a versatile array of applications. For the purpose of better tailoring of nanoparticles activities and understanding the correlation between their structures and properties, control over the composition, shape, size and architecture of bimetallic and multimetallic nanomaterials plays an important role on revealing their new or enhanced functions for potentials application. Advance electron microscopy techniques were used to provide atomic scale insights into the structure-properties of different materials: PtPd, Au-Au3Cu, Cu-Pt, AgPd/Pt and AuCu/Pt nanoparticles. The objective of this work is to understand the physical and chemical properties of nanomaterials and describe synthesis, characterization, surface properties and growth mechanism of various bimetallic and multimetallic nanoparticles. The findings have provided us with novel and significant insights into the physical and chemical properties of noble metal nanoparticles. Different synthesis routes allowed us to synthesize bimetallic: Pt-Pd, Au-Au3Cu, Cu-Pt and trimetallic: AgPd/Pt, AuCu/Pt, core-shell and alloyed nanoparticles with monodispersed sizes, controlled shapes and tunable surface properties. For example, we have synthesized the polyhedral PtPd core-shell nanoparticles with octahedral, decahedral, and triangular plates. Decahedral PtPd core-shell structures are novel morphologies for this system. For the first time we fabricated that the Au core and Au3Cu alloyed shell nanoparticles passivated with CuS2 surface layers and characterized by Cs-corrected scanning transmission electron microscopy. The analysis of the high-resolution micrographs reveals that these nanoparticles have decahedral structure with shell periodicity, and that each of the particles is composed by Au core and Au3Cu ordered superlattice alloyed shell surrounded by CuS 2 surface layer. Additionally, we have described both experimental and theoretical methods of

  8. Crystalline monolayer surface of liquid Au-Cu-Si-Ag-Pd: Metallic glass former

    SciTech Connect

    Mechler, S; Yahel, E; Pershan, P S; Meron, M; Lin, B

    2012-02-06

    It is demonstrated by means of x-ray synchrotron reflectivity and diffraction that the surface of the liquid phase of the bulk metallic glass forming alloy Au49Cu26.9Si16.3Ag5.5Pd2.3 consists of a two-dimensional crystalline monolayer phase for temperatures of up to about 50 K above the eutectic temperature. The present alloy as well as glass forming Au82Si18 and Au-Si-Ge alloys containing small amounts of Ge are the only metallic liquids to exhibit surface freezing well above the melting temperature. This suggests that the phenomena of surface freezing in metallic liquids and glass forming ability are related and probably governed by similar physical properties.

  9. Catalytic activity of bimetallic catalysts highly sensitive to the atomic composition and phase structure at the nanoscale

    NASA Astrophysics Data System (ADS)

    Shan, Shiyao; Petkov, Valeri; Prasai, Binay; Wu, Jinfang; Joseph, Pharrah; Skeete, Zakiya; Kim, Eunjoo; Mott, Derrick; Malis, Oana; Luo, Jin; Zhong, Chuan-Jian

    2015-11-01

    The ability to determine the atomic arrangement in nanoalloy catalysts and reveal the detailed structural features responsible for the catalytically active sites is essential for understanding the correlation between the atomic structure and catalytic properties, enabling the preparation of efficient nanoalloy catalysts by design. Herein we describe a study of CO oxidation over PdCu nanoalloy catalysts focusing on gaining insights into the correlation between the atomic structures and catalytic activity of nanoalloys. PdCu nanoalloys of different bimetallic compositions are synthesized as a model system and are activated by a controlled thermochemical treatment for assessing their catalytic activity. The results show that the catalytic synergy of Pd and Cu species evolves with both the bimetallic nanoalloy composition and temperature of the thermochemical treatment reaching a maximum at a Pd : Cu ratio close to 50 : 50. The nanoalloys are characterized structurally by ex situ and in situ synchrotron X-ray diffraction, including atomic pair distribution function analysis. The structural data show that, depending on the bimetallic composition and treatment temperature, PdCu nanoalloys adopt two different structure types. One features a chemically ordered, body centered cubic (B2) type alloy consisting of two interpenetrating simple cubic lattices, each occupied with Pd or Cu species alone, and the other structure type features a chemically disordered, face-centered cubic (fcc) type of alloy wherein Pd and Cu species are intermixed at random. The catalytic activity for CO oxidation is strongly influenced by the structural features. In particular, it is revealed that the prevalence of chemical disorder in nanoalloys with a Pd : Cu ratio close to 50 : 50 makes them superior catalysts for CO oxidation in comparison with the same nanoalloys of other bimetallic compositions. However, the catalytic synergy can be diminished if the Pd50Cu50 nanoalloys undergo phase

  10. Bimetallic nickel-iron nanoparticles for groundwater decontamination: effect of groundwater constituents on surface deactivation.

    PubMed

    Han, Yanlai; Yan, Weile

    2014-12-01

    The incorporation of catalytic metals on iron nanoparticles to form bimetallic nanoparticles (BNPs) generates a class of highly reactive materials for degrading chlorinated hydrocarbons (e.g., trichloroethylene, TCE) in groundwater. Successful implementation of BNPs to groundwater decontamination relies critically on the stability of surface reactive sites of BNPs in groundwater matrices. This study investigated the effect of common groundwater solutes on TCE reduction with Ni-Fe (with Ni at 2 wt.%) bimetallic nanoparticles (herein denoted as Ni-Fe BNPs). Batch experiments involving pre-exposing the nanoparticles to various groundwater solutions for 24 h followed by reactions with TCE solutions were conducted. The results suggest that the deactivation behavior of Ni-Fe BNPs differs significantly from that of the well-studied Pd-Fe BNPs. Specifically, Ni-Fe BNPs were chemically stable in pure water. Mild reduction in TCE reaction rates were observed for Ni-Fe BNPs pre-exposed to chloride (Cl(-)), bicarbonate (HCO3(-)), sulfite (SO3(2-)) and humic acid solutions. Nitrate (NO3(-)), sulfate (SO4(2-)) and phosphate (HPO4(2-)) may cause moderate to severe deactivation at elevated concentrations (>1 mM). Product analysis and surface chemistry investigations using high-resolution X-ray photoelectron spectroscopy (HR-XPS) reveal that NO3(-) decreased particle reactivity mainly due to progressive formation of passivating oxides, whereas SO4(2-) and phosphate elicited rapid deactivation as a result of specific poisoning of the surface nickel sites. At similar levels, phosphate is the most potent deactivation agent among the solutes examined in this study. While our findings point out the desirable quality of Ni-Fe nanoparticles, particularly their greater electrochemical stability compared to Pd-Fe BNPs, its susceptibility to chemical poisoning at high levels of complexing ligands is also noted. Groundwater chemistry is therefore an important factor to consider when

  11. Low Temperature Hydrogenation of Benzene and Cyclohexene: A Comparative Study Between gamma-Al2O3 Supported PtCo and PtNi Bimetallic Catalysts

    SciTech Connect

    Lu, S.; Lonergan, W; Bosco, J; Wang, S; Zhu, Y; Xie, Y; Chen, J

    2008-01-01

    Supported PtCo and PtNi bimetallic and Co, Ni, Pt monometallic catalysts were prepared by impregnation method on ?-Al2O3 and evaluated for the hydrogenation of benzene and cyclohexene at low temperatures (273-343 K) and atmospheric pressure. Results from batch reactor studies with Fourier transform infrared spectroscopy (FTIR) and flow reactor studies both showed that PtCo bimetallic catalysts exhibited significantly higher activity than PtNi and monometallic Co, Ni, and Pt catalysts for benzene hydrogenation, while PtNi catalysts showed higher activity for cyclohexene hydrogenation. Results from H2 chemisorption and H2-temperature-programmed reduction (H2-TPR) studies showed that a small amount of Pt addition could increase the chemisorption capacity and make the reduction of Co or Ni much easier, especially for Co-based catalysts. Extended X-ray absorption fine structure (EXAFS) results confirmed the formation of Pt-Co and Pt-Ni bimetallic bonds in the PtCo and PtNi bimetallic catalysts, supporting the argument from previous surface science and theoretical predictions that these two bimetallic catalysts would have higher hydrogenation activity than the corresponding monometallic catalysts.

  12. General Method for Determination of the Surface Composition in Bimetallic Nanoparticle Catalysts from the L Edge X-ray Absorption Near-Edge Spectra

    SciTech Connect

    Wu, Tiapin; Childers, David; Gomez, Carolina; Karim, Ayman M.; Schweitzer, Neil; Kropf, Arthur; Wang, Hui; Bolin, Trudy B.; Hu, Yongfeng; Kovarik, Libor; Meyer, Randall; Miller, Jeffrey T.

    2012-10-08

    Bimetallic PtPd on silica nano-particle catalysts have been synthesized and their average structure determined by Pt L3 and Pd K-edge extended X-ray absorption finestructure (EXAFS) spectroscopy. The bimetallic structure is confirmed from elemental line scans by STEM for the individual 1-2 nm sized particles. A general method is described to determine the surface composition in bimetallic nanoparticles even when both metals adsorb, for example, CO. By measuring the change in the L3 X-ray absorption near-edge structure (XANES) spectra with and without CO in bimetallic particles and comparing these changes to those in monometallic particles of known size the fraction of surface atoms can be determined. The turnover rates (TOR) and neopentane hydrogenolysis and isomerization selectivities based on the surface composition suggest that the catalytic and spectroscopic properties are different from those in monometallic nano-particle catalysts. At the same neo-pentane conversion, the isomerization selectivity is higher for the PtPd catalyst while the TOR is lower than that of both Pt and Pd. As with the catalytic performance, the infrared spectra of adsorbed CO are not a linear combination of the spectra on monometallic catalysts. Density functional theory calculations indicate that the Pt-CO adsorption enthalpy increases while the Pd-CO bond energy decreases. The ability to determine the surface composition allows for a better understanding of the spectroscopic and catalytic properties of bimetallic nanoparticle catalysts.

  13. Structural analysis of polymer-protected Pd/Pt bimetallic clusters as dispersed catalysts by using extended x-ray absorption fine structure spectroscopy

    SciTech Connect

    Toshima, Naoki; Harada, Masafumi; Yonezawa, Tetsu; Kushihashi, Kakuta; Asakura, Kiyotaka )

    1991-09-19

    Extended X-ray absorption fine structure (EXAFS) was applied to the determination of the structure of colloidal dispersions of the poly (N-vinyl-2-pyrrolidone)-protected palladium/platinum bimetallic clusters, which work as the catalysts for selective partial hydrogenation of 1,3-cyclooctadiene to cyclooctene. The catalytic activity was found to depend on the structure of the bimetallic clusters. The EXAFS data on the Pd/Pt (4/1) bimetallic clusters, which are the most active catalysts, indicate a Pt core structure, in which the 42 Pd atoms are on the surface of the cluster particle and 13 Pt atoms are at the center of the particle, forming a core. In contrast, the Pd/Pt (1/1) bimetallic clusters are suggested to have a modified Pt core structure, in which 28 Pt atoms connect directly with each other, being located both in the core and on the surface, and 27 Pd atoms form three islands on the surface of the cluster particle. These bimetallic clusters work as active catalysts for selective hydrogenation of olefins, selective partial hydrogenation of diene to monoene, and visible light-induced hydrogen generation from water.

  14. Composite materials formed with anchored nanostructures

    DOEpatents

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2015-03-10

    A method of forming nano-structure composite materials that have a binder material and a nanostructure fiber material is described. A precursor material may be formed using a mixture of at least one metal powder and anchored nanostructure materials. The metal powder mixture may be (a) Ni powder and (b) NiAl powder. The anchored nanostructure materials may comprise (i) NiAl powder as a support material and (ii) carbon nanotubes attached to nanoparticles adjacent to a surface of the support material. The process of forming nano-structure composite materials typically involves sintering the mixture under vacuum in a die. When Ni and NiAl are used in the metal powder mixture Ni.sub.3Al may form as the binder material after sintering. The mixture is sintered until it consolidates to form the nano-structure composite material.

  15. Chemical Sensors Based on Metal Oxide Nanostructures

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Xu, Jennifer C.; Evans, Laura J.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Mike J.; Liu, Chung-Chiun

    2006-01-01

    This paper is an overview of sensor development based on metal oxide nanostructures. While nanostructures such as nanorods show significan t potential as enabling materials for chemical sensors, a number of s ignificant technical challenges remain. The major issues addressed in this work revolve around the ability to make workable sensors. This paper discusses efforts to address three technical barriers related t o the application of nanostructures into sensor systems: 1) Improving contact of the nanostructured materials with electrodes in a microse nsor structure; 2) Controling nanostructure crystallinity to allow co ntrol of the detection mechanism; and 3) Widening the range of gases that can be detected by using different nanostructured materials. It is concluded that while this work demonstrates useful tools for furt her development, these are just the beginning steps towards realizati on of repeatable, controlled sensor systems using oxide based nanostr uctures.

  16. Nanostructured materials for water desalination.

    PubMed

    Humplik, T; Lee, J; O'Hern, S C; Fellman, B A; Baig, M A; Hassan, S F; Atieh, M A; Rahman, F; Laoui, T; Karnik, R; Wang, E N

    2011-07-22

    Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity.

  17. Topology optimization of piezoelectric nanostructures

    NASA Astrophysics Data System (ADS)

    Nanthakumar, S. S.; Lahmer, Tom; Zhuang, Xiaoying; Park, Harold S.; Rabczuk, Timon

    2016-09-01

    We present an extended finite element formulation for piezoelectric nanobeams and nanoplates that is coupled with topology optimization to study the energy harvesting potential of piezoelectric nanostructures. The finite element model for the nanoplates is based on the Kirchoff plate model, with a linear through the thickness distribution of electric potential. Based on the topology optimization, the largest enhancements in energy harvesting are found for closed circuit boundary conditions, though significant gains are also found for open circuit boundary conditions. Most interestingly, our results demonstrate the competition between surface elasticity, which reduces the energy conversion efficiency, and surface piezoelectricity, which enhances the energy conversion efficiency, in governing the energy harvesting potential of piezoelectric nanostructures.

  18. Raman Studies of Carbon Nanostructures

    NASA Astrophysics Data System (ADS)

    Jorio, Ado; Souza Filho, Antonio G.

    2016-07-01

    This article reviews recent advances on the use of Raman spectroscopy to study and characterize carbon nanostructures. It starts with a brief survey of Raman spectroscopy of graphene and carbon nanotubes, followed by recent developments in the field. Various novel topics, including Stokes–anti-Stokes correlation, tip-enhanced Raman spectroscopy in two dimensions, phonon coherence, and high-pressure and shielding effects, are presented. Some consequences for other fields—quantum optics, near-field electromagnetism, archeology, materials and soil sciences—are discussed. The review ends with a discussion of new perspectives on Raman spectroscopy of carbon nanostructures, including how this technique can contribute to the development of biotechnological applications and nanotoxicology.

  19. Nanostructured materials for water desalination

    NASA Astrophysics Data System (ADS)

    Humplik, T.; Lee, J.; O'Hern, S. C.; Fellman, B. A.; Baig, M. A.; Hassan, S. F.; Atieh, M. A.; Rahman, F.; Laoui, T.; Karnik, R.; Wang, E. N.

    2011-07-01

    Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity.

  20. Raman Studies of Carbon Nanostructures

    NASA Astrophysics Data System (ADS)

    Jorio, Ado; Souza Filho, Antonio G.

    2016-07-01

    This article reviews recent advances on the use of Raman spectroscopy to study and characterize carbon nanostructures. It starts with a brief survey of Raman spectroscopy of graphene and carbon nanotubes, followed by recent developments in the field. Various novel topics, including Stokes-anti-Stokes correlation, tip-enhanced Raman spectroscopy in two dimensions, phonon coherence, and high-pressure and shielding effects, are presented. Some consequences for other fields—quantum optics, near-field electromagnetism, archeology, materials and soil sciences—are discussed. The review ends with a discussion of new perspectives on Raman spectroscopy of carbon nanostructures, including how this technique can contribute to the development of biotechnological applications and nanotoxicology.

  1. Coherent acoustic phonons in nanostructures

    NASA Astrophysics Data System (ADS)

    Dekorsy, T.; Taubert, R.; Hudert, F.; Bartels, A.; Habenicht, A.; Merkt, F.; Leiderer, P.; Köhler, K.; Schmitz, J.; Wagner, J.

    2008-02-01

    Phonons are considered as a most important origin of scattering and dissipation for electronic coherence in nanostructures. The generation of coherent acoustic phonons with femtosecond laser pulses opens the possibility to control phonon dynamics in amplitude and phase. We demonstrate a new experimental technique based on two synchronized femtosecond lasers with GHz repetition rate to study the dynamics of coherently generated acoustic phonons in semiconductor heterostructures with high sensitivity. High-speed synchronous optical sampling (ASOPS) enables to scan a time-delay of 1 ns with 100 fs time resolution with a frequency in the kHz range without a moving part in the set-up. We investigate the dynamics of coherent zone-folded acoustic phonons in semiconductor superlattices (GaAs/AlAs and GaSb/InAs) and of coherent vibration of metallic nanostructures of non-spherical shape using ASOPS.

  2. Thermoelectric effects in graphene nanostructures

    NASA Astrophysics Data System (ADS)

    Dollfus, Philippe; Nguyen, Viet Hung; Saint-Martin, Jérôme

    2015-04-01

    The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics.

  3. Thermoelectric effects in graphene nanostructures.

    PubMed

    Dollfus, Philippe; Hung Nguyen, Viet; Saint-Martin, Jérôme

    2015-04-10

    The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics.

  4. Insulating oxide surfaces and nanostructures

    NASA Astrophysics Data System (ADS)

    Goniakowski, Jacek; Noguera, Claudine

    2016-03-01

    This contribution describes some peculiarities of the science of oxide surfaces and nanostructures and proposes a simple conceptual scheme to understand their electronic structure, in the spirit of Jacques Friedel's work. Major results on the effects of non-stoichiometry and polarity are presented, for both semi-infinite surfaces and ultra-thin films, and promising lines of research for the near future are sketched. xml:lang="fr"

  5. Nanostructural engineering of organic aerogels

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.; Lu, X.; Caps, R.; Frocle, J.

    1995-03-01

    Aerogels are a special class of open-cell foams with an ultrafine cell/pore size (<50 nm), high surface area (400-1100 M{sup 2}/g), and a solid matrix composed of interconnected colloidal-like particles or fibers with characteristic diameters of 10 nm. This paper examines the correlation between nanostructure and thermal conductivity in a series of resorcinol-formaldehyde (RF) aerogels prepared under different synthetic conditions.

  6. Simulated study of plasmonic coupling in noble bimetallic alloy nanosphere arrays

    NASA Astrophysics Data System (ADS)

    Bansal, Amit; Verma, S. S.

    2014-05-01

    The plasmonic coupling between the interacting noble metal nanoparticles plays an important role to influence the optical properties of arrays. In this work, we have extended the Mie theory results of our recent communication to include the effect of particle interactions between the alloy nanoparticles by varying interparticle distance and number of particles. The localized surface plasmon resonance (LSPR) peak position, full width at half maxima (FWHM) and scattering efficiency of one dimensional (1D) bimetallic alloy nanosphere (BANS) arrays of earlier optimized compositions i.e. Ag0.75Au0.25, Au0.25Cu0.75 and Ag0.50Cu0.50 have been studied presently by using discrete dipole approximation (DDA) simulations. Studies have been made to optimize size of the nanosphere, number of spheres in the arrays, material and the interparticle distance. It has been found that both the scattering efficiency and FWHM (bandwidth) can be controlled in the large region of the electromagnetic (EM) spectrum by varying the number of interacting particles and interparticle distance. In comparison to other alloy arrays, Ag0.50Cu0.50 BANS arrays (each of particle radius 50 nm) shows larger tunability of LSPR with wide bandwidth (essential condition for plasmonic solar cells).

  7. Simulated study of plasmonic coupling in noble bimetallic alloy nanosphere arrays

    SciTech Connect

    Bansal, Amit Verma, S. S.

    2014-05-15

    The plasmonic coupling between the interacting noble metal nanoparticles plays an important role to influence the optical properties of arrays. In this work, we have extended the Mie theory results of our recent communication to include the effect of particle interactions between the alloy nanoparticles by varying interparticle distance and number of particles. The localized surface plasmon resonance (LSPR) peak position, full width at half maxima (FWHM) and scattering efficiency of one dimensional (1D) bimetallic alloy nanosphere (BANS) arrays of earlier optimized compositions i.e. Ag{sub 0.75}Au{sub 0.25}, Au{sub 0.25}Cu{sub 0.75} and Ag{sub 0.50}Cu{sub 0.50} have been studied presently by using discrete dipole approximation (DDA) simulations. Studies have been made to optimize size of the nanosphere, number of spheres in the arrays, material and the interparticle distance. It has been found that both the scattering efficiency and FWHM (bandwidth) can be controlled in the large region of the electromagnetic (EM) spectrum by varying the number of interacting particles and interparticle distance. In comparison to other alloy arrays, Ag{sub 0.50}Cu{sub 0.50} BANS arrays (each of particle radius 50 nm) shows larger tunability of LSPR with wide bandwidth (essential condition for plasmonic solar cells)

  8. Bimetallic poly- and oligo-nuclear complexes based on a rhodium(III) metalloligand

    NASA Astrophysics Data System (ADS)

    Vasilchenko, Danila B.; Venediktov, Anatoliy B.; Korenev, Sergey V.; Filatov, Evgeniy Yu.; Baidina, Iraida A.; Nadolinnyi, Vladimir A.

    2012-10-01

    Interaction of trans-[Rh(i-Nic)4Cl2]3- anions (i-Nic- - isonicotinate anion) with Cuaq2+ and Coaq2+ cations in water has afforded complex salts Co3[Rh(i-Nic)4Cl2]2·17H2O (1) and Cu3[Rh(i-Nic)4Cl2]2·14H2O (2). Oligonuclear character of 1 and 2 has been established. A coordination polymer Cu5[Rh(i-Nic)4Cl2]2(i-Nic)2(OH)2·2H2O (3) has been crystallized by hydrothermal treatment of 2 at 160 °C, and its structure was determined by X-ray structural analysis. EPR data for the complexes has been collected and interpreted. Thermal decomposition of the salts was studied by c-DTA. Bimetallic alloys rhodium-copper and rhodium-cobalt have been obtained as final products of thermal decomposition.

  9. Structural and optical properties of the naked and passivated Al5Au5 bimetallic nanoclusters

    NASA Astrophysics Data System (ADS)

    Grande-Aztatzi, Rafael; Formoso, Elena; Mercero, Jose M.; Matxain, Jon M.; Grabowski, Slawomir J.; Ugalde, Jesus M.

    2016-03-01

    The structural and optical properties of both the naked and passivated bimetallic Al5Au5 nanoclusters have been analyzed based on data obtained from ab initio density functional theory and quantum molecular dynamics simulations. It has been found that the Al5Au5 nanocluster possesses a hollow shaped minimum energy structure with segregated Al and Au layered domains, the former representing the electrophilic domain and the latter the nucleophilic domain. In particular, it has been shown that alkali metal cations attach in the nucleophilic domain and hop from one Au site to the next one in the picoseconds time scale, while anions are bound tightly to the Al atoms of the electrophilic domain. Simulating annealing studies are very suggestive of the proneness of the nanocluster towards coalescence into large cluster units, when the cluster is left unprotected by appropriate ligands. Further passivation studies with NaF salt suggest, nonetheless, the possibility of the isolation of the Al5Au5 cluster in molten salts or ionic liquids.

  10. Novel building units with bimetallic rings in inorganic/organic hybrid chains and layers

    SciTech Connect

    Mahenthirarajah, Thushitha; Li Yang; Lightfoot, Philip

    2009-11-15

    Hydrothermal synthesis has produced three new compounds constructed from novel building units containing vanadium-oxide (or oxyfluoride) subunits linked together via covalently bound cationic copper complexes. Each new compound exhibits novel structural features: [Cu(dipa)][VOF{sub 4}] (1) incorporates a corner-sharing octahedral vanadium(IV) oxyfluoride chain decorated by copper-(2,2'-dipyridyl amine) complexes which form intra-chain bridges. Within a similar reactant system [Cu(dipa)]{sub 2}[V{sub 6}O{sub 17}] (2) is produced, the structure of which exhibits edge-sharing trigonal bipyramidal vanadium(V) 'ladder-like' double chains which are bridged into layers by tetrahedral pyrovanadate dimers together with the copper-(2,2'-dipyridyl amine) complexes. [Cu(py){sub 4}]{sub 2}[V{sub 4}O{sub 12}] (3), is a 2-D structure featuring exclusively tetrahedral vanadium(V) in four-membered ring building blocks, linked through octahedral copper-pyridine complexes to form two crystallographically different bimetallic layers. - Graphical abstract: Hydrothermal synthesis is used to prepare hybrid mixed metal oxides and oxyfluorides with novel extended connectivities

  11. Magnetic properties of bimetallic clusters composed of Gd and transition metals

    NASA Astrophysics Data System (ADS)

    Mukherjee, Prajna; Gupta, Bikash C.; Jena, Puru

    2016-02-01

    Gadolinium, a rare earth metal, is ferromagnetic, while Mn, a transition metal atom, is antiferromagnetic in the bulk phase. Clusters of these elements, however, share some common properties; both exhibit ferrimagnetic behavior and maintain magnetic moments close to their free atomic value. Using density functional theory and generalized gradient approximation for exchange and correlation, we have studied the magnetic properties of bimetallic clusters composed of Gd and Mn to see if they show unusual behavior. The coupling between Gd and Mn spins is found to be antiferromagnetic, while that between Mn atoms is ferromagnetic. Moreover, the bonding between Gd and Mn atoms is stronger than that between the Gd atoms or Mn atoms, thus enabling the possibility of creating more stable magnetic particles. A systematic study of the magnetic and binding properties of clusters composed of Gd atom and other transition metal atoms such as V, Sc, Ti, Cr, Fe, and Co is also carried out to probe the effect of 3d-orbital occupation on magnetic coupling.

  12. Growth and characterization of bimetallic (Na and K) phthalate single crystals

    NASA Astrophysics Data System (ADS)

    Amuthambigai, C.; Mahadevan, C. K.; Sahaya Shajan, X.

    2016-10-01

    Bimetallic (Na and K) phthalate single crystals were grown by the solvent evaporation method and characterized. X-ray diffraction (single crystal and powder), Fourier transform infrared spectral and atomic absorption spectral measurements indicate a centrosymmetric trigonal crystal system (space group Pbar{3}1c) with chemical composition as Na0.51K1.49C8O4H4.H2O. UV-Vis-NIR spectral measurement indicates an optical transmittance of 72 % in the wavelength range 300-1200 nm. The crystal is found to be nonlinear optically active due to local non-centrosymmetry. Thermal and mechanical stabilities of the grown crystal were examined by thermogravimetric and microhardness measurements. Electrical (both AC, with various frequencies ranging from 200 Hz to 200 kHz, and DC) measurements were taken at various temperatures ranging from 30 to 60 °C by the parallel plate capacitor method. The electrical parameters considered are found to increase with the increase in temperature. The AC and DC activation energies were also estimated. The observed high dielectric constants and good second harmonic generation efficiency indicate that the crystal is expected to be useful in capacitor technology and photonic devices.

  13. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix

    PubMed Central

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively. PMID:26750659

  14. Pd-Au bimetallic catalysts: understanding alloy effects from planar models and (supported) nanoparticles.

    SciTech Connect

    Gao, Feng; Goodman, Wayne D.

    2012-12-21

    Pd-Au bimetallic catalysts often display enhanced catalytic activities and selectivities compared with Pd-alone catalysts. This enhancement is often caused by two alloy effects, i.e., ensemble and ligand effects. The ensemble effect is dilution of surface Pd by Au. With increasing surface Au coverages, contiguous Pd ensembles disappear and isolated Pd ensembles form. For certain reactions, for example vinyl acetate synthesis, this effect is responsible for reaction rate enhancement via the formation of highly active surface sites, e.g., isolated Pd pairs. The disappearance of contiguous Pd ensembles also switches off side reactions catalyzed by these sites. This explains selectivity increase of certain reactions, for example direct H2O2 synthesis. The ligand effect is electronic perturbation of Au to Pd. By direct charge transfer or affecting bond length, the ligand effect causes the Pd d band to be more filled and the d-band center away from the Fermi level. Both changes make Pd more "atomic like" therefore binding reactants and products weaker. For certain reactions, this eliminates the so-called "self poisoning" and enhances activity/selectivity.

  15. Carbon-protected bimetallic carbide nanoparticles for a highly efficient alkaline hydrogen evolution reaction.

    PubMed

    Liu, Yipu; Li, Guo-Dong; Yuan, Long; Ge, Lei; Ding, Hong; Wang, Dejun; Zou, Xiaoxin

    2015-02-21

    The hydrogen evolution reaction (HER) is one of the two important half reactions in current water-alkali and chlor-alkali electrolyzers. To make this reaction energy-efficient, development of highly active and durable catalytic materials in an alkaline environment is required. Herein we report the synthesis of carbon-coated cobalt-tungsten carbide nanoparticles that have proven to be efficient noble metal-free electrocatalysts for alkaline HER. The catalyst affords a current density of 10 mA cm(-2) at a low overpotential of 73 mV, which is close to that (33 mV) required by Pt/C to obtain the same current density. In addition, this catalyst operates stably at large current densities (>30 mA cm(-1)) for as long as 18 h, and gives nearly 100% Faradaic yield during alkaline HER. The excellent catalytic performance (activity and stability) of this nanocomposite material is attributed to the cooperative effect between nanosized bimetallic carbide and the carbon protection layer outside the metal carbide. The results presented herein offer the exciting possibility of using carbon-armoured metal carbides for an efficient alkaline HER, although pristine metal carbides are not, generally, chemically stable enough under such strong alkaline conditions.

  16. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix

    NASA Astrophysics Data System (ADS)

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively.

  17. Bimetallic strip for low temperature use. [4-300/sup 0/K

    DOEpatents

    Bussiee, J.F.; Welch, D.O.; Suenaga, M.

    A class of mechanically pre-stressed structures is provided suitably bi-layer strips, consisting of a layer of group 5 transition metals in intimate contact with a layer of an intermetallic compound of transition metals with certain group 3A, 4A or 5A metals or metalloids such as Ga, In, Si, Ge, Sn, As or Sb. The changes of Young's modulus of these bi-layered combinations at temperatures in the region of somewhat above absolute zero provides a useful means of sensing temperature changes. Such bi-metallic strips may be used as control strips in thermostats, or in direct dial reading instruments. The structures are made by preparing a sandwich of a group 5B transition metal strip between the substantially thicker strips of an alloy between copper and a predetermined group 3A, 4A or 5A metal or metalloid, holding the three layers are heated, cooled the copper alloys and is removed. Removing one of the two formed interlayer alloys between the transition metal and the metal previously alloyed with copper remain.

  18. Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution

    PubMed Central

    Lu, Qi; Hutchings, Gregory S.; Yu, Weiting; Zhou, Yang; Forest, Robert V.; Tao, Runzhe; Rosen, Jonathan; Yonemoto, Bryan T.; Cao, Zeyuan; Zheng, Haimei; Xiao, John Q.; Jiao, Feng; Chen, Jingguang G.

    2015-01-01

    A robust and efficient non-precious metal catalyst for hydrogen evolution reaction is one of the key components for carbon dioxide-free hydrogen production. Here we report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the-art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. In addition, the hierarchical porosity of the nanoporous copper-titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface. PMID:25910892

  19. Selective hydrogen production from formic acid decomposition on Pd-Au bimetallic surfaces.

    PubMed

    Yu, Wen-Yueh; Mullen, Gregory M; Flaherty, David W; Mullins, C Buddie

    2014-08-01

    Pd-Au catalysts have shown exceptional performance for selective hydrogen production via HCOOH decomposition, a promising alternative to solve issues associated with hydrogen storage and distribution. In this study, we utilized temperature-programmed desorption (TPD) and reactive molecular beam scattering (RMBS) in an attempt to unravel the factors governing the catalytic properties of Pd-Au bimetallic surfaces for HCOOH decomposition. Our results show that Pd atoms at the Pd-Au surface are responsible for activating HCOOH molecules; however, the selectivity of the reaction is dictated by the identity of the surface metal atoms adjacent to the Pd atoms. Pd atoms that reside at Pd-Au interface sites tend to favor dehydrogenation of HCOOH, whereas Pd atoms in Pd(111)-like sites, which lack neighboring Au atoms, favor dehydration of HCOOH. These observations suggest that the reactivity and selectivity of HCOOH decomposition on Pd-Au catalysts can be tailored by controlling the arrangement of surface Pd and Au atoms. The findings in this study may prove informative for rational design of Pd-Au catalysts for associated reactions including selective HCOOH decomposition for hydrogen production and electro-oxidation of HCOOH in the direct formic acid fuel cell.

  20. High Temperature Plasticity of Bimetallic Magnesium and Aluminum Friction Stir Welded Joints

    NASA Astrophysics Data System (ADS)

    Regev, Michael; El Mehtedi, Mohamad; Cabibbo, Marcello; Quercetti, Giovanni; Ciccarelli, Daniele; Spigarelli, Stefano

    2014-02-01

    The high temperature deformation of a bimetallic AZ31/AA6061 Friction Stir Welded joint was investigated in the present study by constant load creep experiments carried out at 473 K (200 °C). The microstructural analysis revealed the strongly inhomogeneous nature of the weld, which was characterized by an extremely fine grain size in the magnesium-rich zones and by the extensive presence of intermetallic phases. In the high stress regime, the creep strain was concentrated in the refined and particle-rich microstructure of the weld zone, while the AA6061 base metal remained undeformed. In the low stress regime, deformation became more homogeneously distributed between the AZ31 base metal and the weld zone. The creep behavior of the weld was found to obey the constitutive equation describing the minimum creep rate dependence on applied stress for the base AZ31, slightly modified to take into account the finer microstructure and the role of secondary phase particles, i.e., the retardation of grain growth and the obstruction of grain boundary sliding.

  1. Investigation on the Interface Characteristics of Al/Mg Bimetallic Castings Processed by Lost Foam Casting

    NASA Astrophysics Data System (ADS)

    Jiang, Wenming; Li, Guangyu; Fan, Zitian; Wang, Long; Liu, Fuchu

    2016-05-01

    The lost foam casting (LFC) process was used to prepare the A356 aluminum and AZ91D magnesium bimetallic castings, and the interface characteristics of the reaction layer between aluminum and magnesium obtained by the LFC process were investigated in the present work. The results indicate that a uniform and compact interface between the aluminum and magnesium was formed. The reaction layer of the interface with an average thickness of approximately 1000 μm was mainly composed of Al3Mg2 and Al12Mg17 intermetallic compounds, including the Al3Mg2 layer adjacent to the aluminum insert, the Al12Mg17 middle layer, and the Al12Mg17 + δ eutectic layer adjacent to the magnesium base. Meanwhile, the Mg2Si intermetallic compound was also detected in the reaction layer. An oxide film mainly containing C, O, and Mg elements generated at the interface between the aluminum and magnesium, due to the decomposed residue of the foam pattern, the oxidations of magnesium and aluminum alloys as well as the reaction between the magnesium melt and the aluminum insert. The microhardness tests show that the microhardnesses at the interface were obviously higher than those of the magnesium and aluminum base metals, and the Al3Mg2 layer at the interface had a high microhardness compared with the Al12Mg17 and Al12Mg17 + δ eutectic layers, especially the eutectic layer.

  2. Synthesis of a bimetallic catalyst with a modified-peat support

    SciTech Connect

    Bel'kevich, P.I.; Gaiduk, K.A.; Trubilko, E.V.; Bel'skaya, R.I.; Berezovik, G.K.

    1983-11-01

    Granules of oxidized cotton-grass peat with decomposition factors of 40% and 60% were impregnated with cobalt acetate solution and subjected to pyrolysis at 400-800/sup 0/C for 6 hours. These samples were impregnated with copper acetate solution and subjected to further pyrolysis at 300-400/sup 0/C. The influence of the degree of decomposition of the peat and of the temperature of the second pyrolysis stage where formation of the bimetallic carbon catalysts occurs, were investigated using the dehydrogenation of cyclohexanol. At a reaction temperature of 280/sup 0/C, the max cyclohexanone yield corresponds to 60% decomposition of the peat and a high temperature of heat treatment, while high selectivity is characteristic of samples made with the lower decomposition factor. Upon increase of the reaction temperature to 350/sup 0/C and that of the pyrolysis stage II, the degree of decomposition of the peat has little influence on the cyclohexanone yield. 8 references, 1 figure, 2 tables.

  3. Electrochemical way of molybdenum extraction from the Bimetallic systems of Mo-W

    NASA Astrophysics Data System (ADS)

    Kudreeva, L. K.; Nauryzbaev, M. K.; Kurbatov, A. P.; Kamysbaev, D. H.; Adilbekova, A. O.; Mukataeva, Z. S.

    2015-12-01

    Electrochemical dissolution of molybdenum and tungsten was investigated in water- dimethylsulfoxide (DMSO) media at different concentrations of lithium chloride and magnesium perchlorate. The terms of efficient extraction of molybdenum from bimetallic systems of Mo-W have been determined. The polarization curves of the electrooxidation of molybdenum in the solution of 0.25 M LiCl in the DMSO at the different rates of rotations and the scan rate equal to 50 mV/s were obtained. In the presence of the addition of water at the potential of 0.1-0.75 V the small area of polarizability occurs, then with increasing potentials above 1.5 V there is a sharp increase of the oxidation current. Comparison of the current values of anodic dissolution of molybdenum and tungsten showed that the rate of anodic dissolution of molybdenum significantly exceeds the rate of anodic dissolution of tungsten. In the case of molybdenum, the dissolution process is limited by diffusion, in the case of tungsten - by the passive film formation on the electrode surface.

  4. Mass spectrometric and modeling investigations of bimetallic silver-cobalt clusters

    NASA Astrophysics Data System (ADS)

    Janssens, Ewald; van Hoof, Thibaut; Veldeman, Nele; Neukermans, Sven; Hou, Marc; Lievens, Peter

    2006-05-01

    The stability of bimetallic silver-cobalt clusters with less than 50 atoms is studied experimentally and their associated geometries are predicted by classical modeling. The clusters are created by laser vaporization and inert gas condensation. Their mass distribution is analyzed with time-of-flight mass spectrometry. For clusters containing mainly silver, we find strong quantum size effects related to itinerant behavior of the silver and cobalt valence electrons. In the case of clusters containing mainly cobalt, no pronounced size effects appear in the mass spectra. Photofragmentation experiments reveal that neutral silver atom evaporation is the favorable channel, suggesting that the AgCo bonds are weaker than the CoCo bonds. Consistently, and for both sets of clusters, Metropolis Monte-Carlo simulations predict these clusters to have icosahedral based structures that may depend on temperature. In clusters containing mainly silver, cobalt sits at the cluster center and fragmentation proceeds by the evaporation of silver surface atoms. In clusters containing mainly cobalt, silver atoms also locate at the periphery and are more weakly bound to the cluster than cobalt surface atoms.

  5. Electroactive copper(II) bimetallic self-assembled multilayers on Si(100)

    NASA Astrophysics Data System (ADS)

    Sánchez, Alejandra; Urcuyo, Roberto; González-Flores, Diego; Montalberth-Smith, Ricardo; León-Rojas, Carlos; Pineda, Leslie W.; Montero, Mavis L.

    2012-02-01

    Silicon (100) surfaces were modified by reacting 4-aminopyridine and Si-Cl bond. These surfaces were further used for tethering copper bimetallic complexes and growing monolayers and multilayers by changing the axial position via Lewis acid-base reactions. In this way, coordination chemistry approach can be used as building blocks for controlling the design of functional surfaces. Furthermore, the outcomes of the several characterization techniques indicate that the complex is spatially oriented suggesting that this simple strategy allows the preparation of three dimensional molecular structures exhibiting spatial order. The structures on surface show interesting electroactive behaviors leading two cathodic signals, that can be related to Cu(II)/Cu(I) and Cu(I)/Cu(0) electro-reduction species (signals at - 0.15 V and - 0.50 V) and one peak in the anodic region (- 0.15 V) ascribed to the Cu(0)/Cu(II) electro-oxidation reaction, using an Ag/AgCl saturated electrode and platinum wire as reference and counter electrodes, respectively.

  6. [Reduction Kinetics of Cr (VI) in Chromium Contaminated Soil by Nanoscale Zerovalent Iron-copper Bimetallic].

    PubMed

    Ma, Shao-yun; Zhu, Fang; Shang, Zhi-feng

    2016-05-15

    Nanoscale zerovalent iron-copper bimetallic (nZVI/Cu) was produced by liquid-phase reduction and characterized by SEM and XRD. The remediation of Cr (VI) contaminated soil was conducted with nZVI/Cu, and the affecting factors and reduction kinetics were investigated. The results indicated that nZVI/Cu was effective in the degradation of Cr(VI) in soil at an initial pH of 7 at 30'C.After 10 min of reaction, Cr(VI) in the soil was completely degraded when the. concentration of nZVI/Cu was 2 g · L⁻' and the concentration of Cr(VI) in contaminated soil was 88 mg · kg⁻¹. nZVI/Cu amount, pH value, reaction temperature, and the concentration of humic acid affected the degradation of Cr(VI). The removal efficiency of Cr(VI)--increased with increasing reaction temperature and decreased with increasing initial pH value. Humic acid had a certain impact on the degradation of Cr(W) in soil. The removal of Cr (VI) followed the pseudo first order reduction kinetics model, and the relationship between the reduction rate and the reaction temperature accorded with Arrhenius law, and the reaction activation energy (Ea) was 104.26 kJ · mol⁻¹.

  7. [Reduction Kinetics of Cr (VI) in Chromium Contaminated Soil by Nanoscale Zerovalent Iron-copper Bimetallic].

    PubMed

    Ma, Shao-yun; Zhu, Fang; Shang, Zhi-feng

    2016-05-15

    Nanoscale zerovalent iron-copper bimetallic (nZVI/Cu) was produced by liquid-phase reduction and characterized by SEM and XRD. The remediation of Cr (VI) contaminated soil was conducted with nZVI/Cu, and the affecting factors and reduction kinetics were investigated. The results indicated that nZVI/Cu was effective in the degradation of Cr(VI) in soil at an initial pH of 7 at 30'C.After 10 min of reaction, Cr(VI) in the soil was completely degraded when the. concentration of nZVI/Cu was 2 g · L⁻' and the concentration of Cr(VI) in contaminated soil was 88 mg · kg⁻¹. nZVI/Cu amount, pH value, reaction temperature, and the concentration of humic acid affected the degradation of Cr(VI). The removal efficiency of Cr(VI)--increased with increasing reaction temperature and decreased with increasing initial pH value. Humic acid had a certain impact on the degradation of Cr(W) in soil. The removal of Cr (VI) followed the pseudo first order reduction kinetics model, and the relationship between the reduction rate and the reaction temperature accorded with Arrhenius law, and the reaction activation energy (Ea) was 104.26 kJ · mol⁻¹. PMID:27506053

  8. Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution

    SciTech Connect

    Lu, Qi; Hutchings, Gregory S.; Yu, Weiting; Zhou, Yang; Forest, Robert V.; Tao, Runzhe; Rosen, Jonathan; Yonemoto, Bryan T.; Cao, Zeyuan; Zheng, Haimei; Xiao, John Q.; Jiao, Feng; Chen, Jingguang G.

    2015-03-16

    One of the key components of carbon dioxide-free hydrogen production is a robust and efficient non-precious metal catalyst for the hydrogen evolution reaction. We report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the- art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. Moreover, the hierarchical porosity of the nanoporous-copper titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.

  9. Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution

    DOE PAGES

    Lu, Qi; Hutchings, Gregory S.; Yu, Weiting; Zhou, Yang; Forest, Robert V.; Tao, Runzhe; Rosen, Jonathan; Yonemoto, Bryan T.; Cao, Zeyuan; Zheng, Haimei; et al

    2015-03-16

    One of the key components of carbon dioxide-free hydrogen production is a robust and efficient non-precious metal catalyst for the hydrogen evolution reaction. We report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the- art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. Moreover, the hierarchicalmore » porosity of the nanoporous-copper titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.« less

  10. Bimetallic silver-gold clusters by matrix-assisted laser desorption/ionization.

    PubMed

    Kéki, Sándor; Nagy, Lajos; Deák, György; Zsuga, Miklós

    2004-10-01

    Pure gold clusters (Aun+) were produced up to the cluster size of n = 100 by matrix-assisted laser desorption/ionization (MALDI). The mass spectrum of the resulting clusters showed alteration in the ion intensity at odd-even clusters size. On the other hand, intensity drops at cluster size predicted by the jellium model theory was also observed. Positively and negatively charged bimetallic silver-gold clusters were produced under MALDI conditions from the mixture of HAuCl4/silver trifluoroacetate and the 2-(4-hydroxyphenylazo)benzoic acid (HABA) matrix. A linear correlation was found between the intensity ratio of AunAgm+ to Au(n+1)Ag(m-1)+ cluster ions and the molar ratio of the gold to silver salt. It was observed that the composition and the distribution of the clusters can be varied with the molar ratio of the silver and gold salts. It was also found that the resulting cluster sizes obey the lognormal distribution. PMID:15465358

  11. Cryogenic tests of bimetallic diamond-turned mirrors for the FRIDA integral field unit

    NASA Astrophysics Data System (ADS)

    DeWitt, Curtis; Eikenberry, Stephen; Cuevas Cardona, Salvador; Chapa, Oscar; Espejo, Carlos; Keiman, Carolina; Sanchez, Beatriz

    2008-07-01

    We describe diamond-turned material tests for the integral field unit (IFU) for the FRIDA instrument (inFRared Imager and Dissector for the Adaptive optics system of the Gran Telescopio Canarias). FRIDA is closely based on the design of the successful FISICA cryogenic infrared image slicing device, which used "monolithic" mirror arrays, diamond turned into single pieces of metal. FRIDA, however, will require better roughness characteristics than the 15nm RMS of FISICA to avoid light scatter in FRIDA's shorter wavelength limit (900nm). Al 6061 seems to be limited to this roughness level by its silicate inclusions so some new combination of materials that are compatible with FRIDA's Al 6061 structure must be found. To this end, we have tested six diamond-turned mirrors with different materials and different platings. We used the Zygo interferometer facility at IA-UNAM to do warm and cold profile measurements of the mirrors to investigate possible bimetallic deformation effects. We present a detailed comparison of the various performance characteristics of the test mirrors.

  12. Thermodynamic parameters governing the self-assembly of head-head-head lanthanide bimetallic helicates.

    PubMed

    Jensen, Thomas B; Scopelliti, Rosario; Bünzli, Jean-Claude G

    2007-01-01

    The heterobitopic ligands L ABX (X=1, 2, 3, 4 or 5), differing only by a Cl or NEt(2) substituent, have been designed to complex with a pair of lanthanide ions to form triple-stranded bimetallic helicates of overall composition [Ln2(L ABX)3]6+. The percentage of HHH (head-head-head) isomer, in which each of the three ligand strands coordinates to the same lanthanide ion with the same coordination unit, is deciding the ability of the ligands to selectively form heterobimetallic complexes containing one luminescent and one magnetic or two different luminescent ions. It deviates significantly from the statistical value of 25 % and ranges from 6-20 % for L AB2 complexes to 93-96 % for L AB4 complexes. The equilibrium between HHT (head-head-tail) and HHH isomers has been investigated in detail for homobimetallic helicates (Ln=Y, La, Ce, Pr, Nd, Sm, Eu, Lu) by means of variable temperature NMR and thermodynamic parameters have been determined. The equilibrium is characterized by small values of DeltaH and DeltaS, which vary in opposite direction along the lanthanide series for complexes with the same ligand in a way that keeps the value of DeltaG almost constant. The results are interpreted in terms of differences in interstrand stacking, ion-dipole interactions and metal-metal repulsion. PMID:17600785

  13. Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Lu, Qi; Hutchings, Gregory S.; Yu, Weiting; Zhou, Yang; Forest, Robert V.; Tao, Runzhe; Rosen, Jonathan; Yonemoto, Bryan T.; Cao, Zeyuan; Zheng, Haimei; Xiao, John Q.; Jiao, Feng; Chen, Jingguang G.

    2015-03-01

    A robust and efficient non-precious metal catalyst for hydrogen evolution reaction is one of the key components for carbon dioxide-free hydrogen production. Here we report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the-art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. In addition, the hierarchical porosity of the nanoporous copper-titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.

  14. Molybdenum-Bismuth Bimetallic Chalcogenide Nanosheets for Highly Efficient Electrocatalytic Reduction of Carbon Dioxide to Methanol.

    PubMed

    Sun, Xiaofu; Zhu, Qinggong; Kang, Xinchen; Liu, Huizhen; Qian, Qingli; Zhang, Zhaofu; Han, Buxing

    2016-06-01

    Methanol is a very useful platform molecule and liquid fuel. Electrocatalytic reduction of CO2 to methanol is a promising route, which currently suffers from low efficiency and poor selectivity. Herein we report the first work to use a Mo-Bi bimetallic chalcogenide (BMC) as an electrocatalyst for CO2 reduction. By using the Mo-Bi BMC on carbon paper as the electrode and 1-butyl-3-methylimidazolium tetrafluoroborate in MeCN as the electrolyte, the Faradaic efficiency of methanol could reach 71.2 % with a current density of 12.1 mA cm(-2) , which is much higher than the best result reported to date. The superior performance of the electrode resulted from the excellent synergistic effect of Mo and Bi for producing methanol. The reaction mechanism was proposed and the reason for the synergistic effect of Mo and Bi was discussed on the basis of some control experiments. This work opens a way to produce methanol efficiently by electrochemical reduction of CO2 . PMID:27098284

  15. Supported Pd/Sn bimetallic nanoparticles for reductive dechlorination of aqueous trichloroethylene.

    PubMed

    Lin, Chin Jung; Liou, Ya Hsuan; Lo, Shang-Lien

    2009-01-01

    A Pd/Sn bimetallic nanoparticles resin (nano-Pd/Sn/resin) was successfully synthesized for reductive transformation of aqueous trichloroethylene (TCE). The physicochemical properties of the prepared resin were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, N(2) isothermal sorption at and X-ray photospectroscopy. The surface-area-normalized rate constants (k(SA)) of Sn particles in the nanoscale range (50-100 nm) were 4.5 times larger than the k(SA) for powdered Sn (0.04 mm). After depositing 1 wt% Pd onto nano-Sn surface, k(SA) was further enhanced by about a factor of 2. Groundwater constituents such as sulfide nitrate and dissolved oxygen had significant negative effects on the rate of TCE degradation by the nano-Pd/Sn/resin. A wet-chemical method regeneration method was observed to effectively restore the reactivity of the poisoned nano-Pd/Sn/resin after dipping in sulfide solution for 2d. In all cases, less than 0.5% of the degraded TCE appeared as chlorinated byproducts including the three dichloroethene isomers. The nano-Pd/Sn/resin technique performs well in transforming TCE into nontoxic hydrocarbons, as compared with other published methods.

  16. Catalytic dechlorination of Aroclor 1242 by Ni/Fe bimetallic nanoparticles.

    PubMed

    Zhang, Zhen; Hu, Sai; Baig, Shams Ali; Tang, Jie; Xu, Xinhua

    2012-11-01

    Ni/Fe bimetallic nanoparticles were synthesized for treatment of Aroclor 1242, in order to evaluate their applicability for in situ remediation of groundwater and soil contaminated by polychlorinated biphenyls (PCBs). Our experimental results indicate that the total PCB concentration changed during the reduction of 3,5-dichlorobiphenyl (PCB 14), and biphenyl was produced as the final product. Initially, the concentration of 3-chlorobiphenyl (PCB 2) was increased in the prophase reaction and then slowly decreased, suggesting that Aroclor 1242 was first adsorbed by Ni/Fe nanoparticles, and then, the higher chlorinated congeners were converted gradually to the lower chlorinated congeners, and finally to biphenyl. The dechlorination efficiency of Aroclor 1242 reached approximately 80% at 25°C in just 5h, then 95.6% and 95.8% in 10h and 24h, respectively. The study revealed that high Ni/Fe nanoparticle dosage and high Ni content in Ni/Fe nanoparticles favor the catalytic dechlorination reaction. Moreover, a comparison of different types of catalysts on the dechlorination of Aroclor 1242 indicated that Ni/Mg and Mg powders showed a greater reactivity than Ni/Fe and Fe nanoparticles, respectively.

  17. Application of smart nanostructures in medicine.

    PubMed

    He, Jingjing; Qi, Xiaoxue; Miao, Yuqing; Wu, Hai-Long; He, Nongyue; Zhu, Jun-Jie

    2010-09-01

    Smart nanostructures are sensitive to various environmental or biological parameters. They offer great potential for numerous biomedical applications such as monitoring, diagnoses, repair and treatment of human biological systems. The present work introduces smart nanostructures for biomedical applications. In addition to drug delivery, which has been extensively reported and reviewed, increasing interest has been observed in using smart nanostructures to develop various novel techniques of sensing, imaging, tissue engineering, biofabrication, nanodevices and nanorobots for the improvement of healthcare.

  18. Photoinduced magnetic force between nanostructures

    NASA Astrophysics Data System (ADS)

    Guclu, Caner; Tamma, Venkata Ananth; Wickramasinghe, Hemantha Kumar; Capolino, Filippo

    2015-12-01

    Photoinduced magnetic force between nanostructures, at optical frequencies, is investigated theoretically. Till now optical magnetic effects were not used in scanning probe microscopy because of the vanishing natural magnetism with increasing frequency. On the other hand, artificial magnetism in engineered nanostructures led to the development of measurable optical magnetism. Here two examples of nanoprobes that are able to generate strong magnetic dipolar fields at optical frequency are investigated: first, an ideal magnetically polarizable nanosphere and then a circular cluster of silver nanospheres that has a looplike collective plasmonic resonance equivalent to a magnetic dipole. Magnetic forces are evaluated based on nanostructure polarizabilities, i.e., induced magnetic dipoles, and magnetic-near field evaluations. As an initial assessment on the possibility of a magnetic nanoprobe to detect magnetic forces, we consider two identical magnetically polarizable nanoprobes and observe magnetic forces on the order of piconewtons, thereby bringing it within detection limits of conventional atomic force microscopes at ambient pressure and temperature. The detection of magnetic force is a promising method in studying optical magnetic transitions that can be the basis of innovative spectroscopy applications.

  19. Optical properties of chiral nanostructures

    NASA Astrophysics Data System (ADS)

    Cecilia, Noguez; Román-Velázquez, Carlos E.; Garzón, Ignacio L.

    2004-03-01

    We present a computational model to study the optical properties chiral nanostructures[1] . In this work the nanostructures of interest are composed by N atoms, where each one is represented by a polarizable point dipole located at theposition of the atom. We assume that the dipole located is characterized by a polarizability. The nanostructure is excited by a circularly polarized incident wave, such that, each dipole is subject to a total electric field due to: (i) the incident radiation field, plus (ii) the radiation field resulting from all of the other induced dipoles. Once we solve the complex-linear equations, the dipole moment on each atom in the cluster can be determined and we can find the extinction cross section of the whole nanoparticle. Circular dichroism (CD) spectra of chiral bare and thiol-passivated gold nanoclusters have been calculated within the dipole approximation. The calculated CD spectra show features that allow us to distinguish between clusters with different indexes of chirality. The main factor responsible of the differences in the CD lineshapes is the distribution of interatomic distances that characterize the chiral cluster geometry. These results provide theoretical support for the quantification of chirality and its measurement, using the CD lineshapes of chiral metal nanoclusters. [1] C. E. Roman-Velazquez, et al., J. of Phys. Chem. B (Letter) 107, 12035 (2003) This work has been partly supported by DGAPA-UNAM grants No. IN104201 and IN104402, and by CONACyT grant 36651-E.

  20. Physical electrochemistry of nanostructured devices.

    PubMed

    Bisquert, Juan

    2008-01-01

    This Perspective reviews recent developments in experimental techniques and conceptual methods applied to the electrochemical properties of metal-oxide semiconductor nanostructures and organic conductors, such as those used in dye-sensitized solar cells, high-energy batteries, sensors, and electrochromic devices. The aim is to provide a broad view of the interpretation of electrochemical and optoelectrical measurements for semiconductor nanostructures (sintered colloidal particles, nanorods, arrays of quantum dots, etc.) deposited or grown on a conducting substrate. The Fermi level displacement by potentiostatic control causes a broad change of physical properties such as the hopping conductivity, that can be investigated over a very large variation of electron density. In contrast to traditional electrochemistry, we emphasize that in nanostructured devices we must deal with systems that depart heavily from the ideal, Maxwell-Boltzmann statistics, due to broad distributions of states (energy disorder) and interactions of charge carriers, therefore the electrochemical analysis must be aided by thermodynamics and statistical mechanics. We discuss in detail the most characteristic densities of states, the chemical capacitance, and the transport properties, specially the chemical diffusion coefficient, mobility, and generalized Einstein relation.

  1. Chitosan in nanostructured thin films.

    PubMed

    Pavinatto, Felippe J; Caseli, Luciano; Oliveira, Osvaldo N

    2010-08-01

    This review paper brings an overview of the use of chitosans in nanostructured films produced with the Langmuir-Blodgett (LB) or the electrostatic layer-by-layer (LbL) techniques, with emphasis on their possible applications. From a survey in the literature one may identify three main types of study with chitosan in nanostructured films. First, the interaction between chitosans and phospholipid Langmuir monolayers has been investigated for probing the mechanisms of chitosan action in their biological applications, with the monolayers serving as cell membrane models. In the second type, chitosan serves as a matrix for immobilization of biomolecules in LB as well as in LbL films, for which chitosan is suitable to help preserve the bioactivity of such biomolecules for long periods of time even in dry, solid films. An important application of these chitosan-containing films is in sensing and biosensing. The third type of study involves exploiting the mechanical and biocompatibility properties of chitosan in producing films with enhanced properties, for example, for tissue engineering. It is emphasized that chitosans have been proven excellent building blocks to produce films with controlled molecular architecture, allowing for synergy between distinct materials. We also discuss the prospects of the field, following a critical review of the latest developments in nanostructured chitosan films. PMID:20590156

  2. Ag/Au bi-metallic film based color surface plasmon resonance biosensor with enhanced sensitivity, color contrast and great linearity.

    PubMed

    Li, Chung-Tien; Lo, Kun-Chi; Chang, Hsin-Yun; Wu, Hsieh-Ting; Ho, Jennifer H; Yen, Ta-Jen

    2012-01-01

    In wavelength surface plasmon resonance (SPR) biosensor, the manipulation of SPR dispersion relation by Ag/Au bi-metallic film was first time implemented. Due to the enhanced resonant wavelength shift and the sharper SPR slope of using Ag/Au bi-metallic film, the illuminated color of reflection shows one order of magnitude greater contrast than conventional SPR biosensors. Such an Ag/Au bi-metallic film based color SPR biosensor (CSPRB) allows the detail bio-interactions, for example 100 nM streptavidin, to be distinguished by directly observing the color change of reflection through naked eyes rather than the analysis of spectrometer. In addition to the enhanced sensitivity and color contrast, this CSPRB also possesses a great linear detection range up to 0.0254 RIU, which leading to the application of point-of-care tests. PMID:22560104

  3. Effect of pretreatment conditions on particle size of bimetallic pt-au catalysts supported on ZnO/Al2O3 and its activity for toluene oxidation.

    PubMed

    Kim, Ki-Joong; Kang, Sang-Jun; Chung, Min-Chul; Jung, Sang-Chul; Jeong, Woon-Jo; Park, Gye-Choon; Kim, Sang-Chai; Boo, Su-Il; Jeong, Seung-Won; Ahn, Ho-Geun

    2010-09-01

    Bimetallic Pt-Au catalysts supported on ZnO/Al2O3 were prepared by incipient wetness impregnation (IW-IMP) method with different pretreatment conditions such as flow velocity, calcination temperature, and heating rate under H2 during the calcination procedure, and characterized by X-ray diffraction (XRD), CO chemisorption, and scanning transmission electron microscopy (STEM) equipped energy dispersive spectroscopy (EDS). Furthermore, catalytic activity for complete oxidation of toluene was measured using a flow reactor under atmospheric pressure. Finally, relationship between the particle sizes with pretreatment conditions and catalytic activity for toluene on the bimetallic Pt-Au catalysts was discussed. In these results, nanosized bimetallic Pt-Au particles on ZnO/Al2O3 could be prepared by IW-IMP method. Relationship between the Pt and Au particle size and activity for toluene oxidation was clearly observed. PMID:21133118

  4. Synthesis of Silver Nanostructures by Multistep Methods

    PubMed Central

    Zhang, Tong; Song, Yuan-Jun; Zhang, Xiao-Yang; Wu, Jing-Yuan

    2014-01-01

    The shape of plasmonic nanostructures such as silver and gold is vital to their physical and chemical properties and potential applications. Recently, preparation of complex nanostructures with rich function by chemical multistep methods is the hotspot of research. In this review we introduce three typical multistep methods to prepare silver nanostructures with well-controlled shapes, including the double reductant method, etching technique and construction of core-shell nanostructures. The growth mechanism of double the reductant method is that different favorable facets of silver nanocrystals are produced in different reductants, which can be used to prepare complex nanostructures such as nanoflags with ultranarrow resonant band bandwidth or some silver nanostructures which are difficult to prepare using other methods. The etching technique can selectively remove nanoparticles to achieve the aim of shape control and is widely used for the synthesis of nanoflowers and hollow nanostructures. Construction of core-shell nanostructures is another tool to control shape and size. The three methods can not only prepare various silver nanostructures with well-controlled shapes, which exhibit unique optical properties, such as strong surface-enhanced Raman scattering (SERS) signal and localized surface plasmon resonance (LSPR) effect, but also have potential application in many areas. PMID:24670722

  5. Thermodynamics and Kinetics of DNA Nanostructure Assembly

    NASA Astrophysics Data System (ADS)

    Nangreave, Jeanette

    2011-12-01

    The unique structural features of deoxyribonucleic acid (DNA) that are of considerable biological interest also make it a valuable engineering material. Perhaps the most useful property of DNA for molecular engineering is its ability to self-assemble into predictable, double helical secondary structures. These interactions are exploited to design a variety of DNA nanostructures, which can be organized into both discrete and periodic structures. This dissertation focuses on studying the dynamic behavior of DNA nanostructure recognition processes. The thermodynamics and kinetics of nanostructure binding are evaluated, with the intention of improving our ability to understand and control their assembly. Presented here are a series of studies toward this goal. First, multi-helical DNA nanostructures were used to investigate how the valency and arrangement of the connections between DNA nanostructures affect super-structure formation. The study revealed that both the number and the relative position of connections play a significant role in the stability of the final assembly. Next, several DNA nanostructures were designed to gain insight into how small changes to the nanostructure scaffolds, intended to vary their conformational flexibility, would affect their association equilibrium. This approach yielded quantitative information about the roles of enthalpy and entropy in the affinity of polyvalent DNA nanostructure interactions, which exhibit an intriguing compensating effect. Finally, a multi-helical DNA nanostructure was used as a model 'chip' for the detection of a single stranded DNA target. The results revealed that the rate constant of hybridization is strongly dominated by a rate-limiting nucleation step.

  6. Processing Nanostructured Sensors Using Microfabrication Techniques

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; VanderWal, Randall L.; Evans, Laura J.; Xu, Jennifer C.

    2010-01-01

    Standard microfabrication techniques can be implemented and scaled to help assemble nanoscale microsensors. Currently nanostructures are often deposited onto materials primarily by adding them to a solution, then applying the solution in a thin film. This results in random placement of the nanostructures with no controlled order, and no way to accurately reproduce the placement. This method changes the means by which microsensors with nanostructures are fabricated. The fundamental advantage to this approach is that it enables standard microfabrication techniques to be applied in the repeated manufacture of nanostructured sensors on a microplatform.

  7. Nanostructures having crystalline and amorphous phases

    DOEpatents

    Mao, Samuel S; Chen, Xiaobo

    2015-04-28

    The present invention includes a nanostructure, a method of making thereof, and a method of photocatalysis. In one embodiment, the nanostructure includes a crystalline phase and an amorphous phase in contact with the crystalline phase. Each of the crystalline and amorphous phases has at least one dimension on a nanometer scale. In another embodiment, the nanostructure includes a nanoparticle comprising a crystalline phase and an amorphous phase. The amorphous phase is in a selected amount. In another embodiment, the nanostructure includes crystalline titanium dioxide and amorphous titanium dioxide in contact with the crystalline titanium dioxide. Each of the crystalline and amorphous titanium dioxide has at least one dimension on a nanometer scale.

  8. Anchored nanostructure materials and method of fabrication

    DOEpatents

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2012-11-27

    Anchored nanostructure materials and methods for their fabrication are described. The anchored nanostructure materials may utilize nano-catalysts that include powder-based or solid-based support materials. The support material may comprise metal, such as NiAl, ceramic, a cermet, or silicon or other metalloid. Typically, nanoparticles are disposed adjacent a surface of the support material. Nanostructures may be formed as anchored to nanoparticles that are adjacent the surface of the support material by heating the nano-catalysts and then exposing the nano-catalysts to an organic vapor. The nanostructures are typically single wall or multi-wall carbon nanotubes.

  9. Precise replication of antireflective nanostructures from biotemplates

    NASA Astrophysics Data System (ADS)

    Gao, Hongjun; Liu, Zhongfan; Zhang, Jin; Zhang, Guoming; Xie, Guoyong

    2007-03-01

    The authors report herein a new type of nanonipple structures on the cicada's eye and the direct structural replication of the complex micro- and nanostructures for potential functional emulation. A two-step direct molding process is developed to replicate these natural micro- and nanostructures using epoxy resin with high fidelity, which demonstrates a general way of fabricating functional nanostructures by direct replication of natural biotemplates via a suitable physicochemical process. Measurements of spectral reflectance showed that this kind of replicated nanostructure has remarkable antireflective property, suggestive of its potential applications to optical devices.

  10. Nanostructures created by interfered femtosecond laser

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Chang, Yun-Ching; Yao, Jimmy; Luo, Claire; Yin, Shizhuo; Ruffin, Paul; Brantley, Christina; Edwards, Eugene

    2011-10-01

    The method by applying the interfered femtosecond laser to create nanostructured copper (Cu) surface has been studied. The nanostructure created by direct laser irradiation is also realized for comparison. Results show that more uniform and finer nanostructures with sphere shape and feature size around 100 nm can be induced by the interfered laser illumination comparing with the direct laser illumination. This offers an alternative fabrication approach that the feature size and the shape of the laser induced metallic nanostructures can be highly controlled, which can extremely improve its performance in related application such as the colorized metal, catalyst, SERS substrate, and etc.

  11. Growth and characterizations of organized nanostructures

    NASA Astrophysics Data System (ADS)

    Lee, Ji Hoon

    The research investigations and progresses in nanotechnology and the efforts to fabricate novel nanostructures are expected to provide new perspectives into the understanding of underlying science and the formation mechanisms of nanostructures and thus providing the potential for the next-generation device applications. The potential impact of the nano-devices to our society could be extremely enormous and thus the fabrication, engineering and designing of new configuration of nanostructures have attracted a tremendous attention from a number of research fields. In Chapter 1, a brief introduction to the growth & characterization of organized nanostructures is given. Chapter 2 discusses about the growth and fabrication effort of localized quantum structures by using Stranski-Krastanov (SK) growth model on shallow patterns (35nm), namely quantum dots, quantum dot chain, quantum wires and the related research. Chapter 3 introduces the growth and characterization of novel nanostructures using Volmer-Weber (V-W) growth model. More specifically, the formation of metal droplets, the fabrication of ring-shaped nanostructures and various configurations of nanostructures using droplet epitaxy are presented. Chapter 4 explains the formation mechanisms and the optical properties of quantum dot molecules (QDMs), a hybrid nanostructure composed of a pair of a metal particle, a semiconductor quantum ring (QR), and various advanced nanostructures. Chapter 5 concludes the dissertation with some concluding remarks.

  12. Modeling energy transport in nanostructures

    NASA Astrophysics Data System (ADS)

    Pattamatta, Arvind

    Heat transfer in nanostructures differ significantly from that in the bulk materials since the characteristic length scales associated with heat carriers, i.e., the mean free path and the wavelength, are comparable to the characteristic length of the nanostructures. Nanostructure materials hold the promise of novel phenomena, properties, and functions in the areas of thermal management and energy conversion. Example of thermal management in micro/nano electronic devices is the use of efficient nanostructured materials to alleviate 'hot spots' in integrated circuits. Examples in the manipulation of heat flow and energy conversion include nanostructures for thermoelectric energy conversion, thermophotovoltaic power generation, and data storage. One of the major challenges in Metal-Oxide Field Effect Transistor (MOSFET) devices is to study the 'hot spot' generation by accurately modeling the carrier-optical phonon-acoustic phonon interactions. Prediction of hotspot temperature and position in MOSFET devices is necessary for improving thermal design and reliability of micro/nano electronic devices. Thermoelectric properties are among the properties that may drastically change at nanoscale. The efficiency of thermoelectric energy conversion in a material is measured by a non-dimensional figure of merit (ZT) defined as, ZT = sigmaS2T/k where sigma is the electrical conductivity, S is the Seebeck coefficient, T is the temperature, and k is the thermal conductivity. During the last decade, advances have been made in increasing ZT using nanostructures. Three important topics are studied with respect to energy transport in nanostructure materials for micro/nano electronic and thermoelectric applications; (1) the role of nanocomposites in improving the thermal efficiency of thermoelectric devices, (2) the interfacial thermal resistance for the semiconductor/metal contacts in thermoelectric devices and for metallic interconnects in micro/nano electronic devices, (3) the

  13. Immobilization of ultrafine bimetallic Ni-Pt nanoparticles inside the pores of metal-organic frameworks as efficient catalysts for dehydrogenation of alkaline solution of hydrazine.

    PubMed

    Cao, Nan; Yang, Lan; Dai, Hongmei; Liu, Teng; Su, Jun; Wu, Xiaojun; Luo, Wei; Cheng, Gongzhen

    2014-10-01

    We report a facile liquid impregnation approach for immobilization of ultrafine bimetallic Ni-Pt nanoparticles (NPs) inside the pores of MIL-101. The methods of powder X-ray diffraction, N2 physisorption, X-ray photoelectron spectroscopy, transmission electron microscopy, and inductively coupled plasma-atomic emission spectroscopy were employed to characterize the NiPt@MIL-101 catalysts and further indicated the as-synthesized Ni-Pt NPs were confined in the pores of MIL-101. These as-synthesized bimetallic NiPt@MIL-101 NPs exhibit exceedingly high catalytic activity, selectivity, and durability toward hydrogen generation from alkaline solution of hydrazine. PMID:25197778

  14. Material property evaluations of bimetallic welds, stainless steel saw fusion lines, and materials affected by dynamic strain aging

    SciTech Connect

    Rudland, D.; Scott, P.; Marschall, C.; Wilkowski, G.

    1997-04-01

    Pipe fracture analyses can often reasonably predict the behavior of flawed piping. However, there are material applications with uncertainties in fracture behavior. This paper summarizes work on three such cases. First, the fracture behavior of bimetallic welds are discussed. The purpose of the study was to determine if current fracture analyses can predict the response of pipe with flaws in bimetallic welds. The weld joined sections of A516 Grade 70 carbon steel to F316 stainless steel. The crack was along the carbon steel base metal to Inconel 182 weld metal fusion line. Material properties from tensile and C(T) specimens were used to predict large pipe response. The major conclusion from the work is that fracture behavior of the weld could be evaluated with reasonable accuracy using properties of the carbon steel pipe and conventional J-estimation analyses. However, results may not be generally true for all bimetallic welds. Second, the toughness of austenitic steel submerged-arc weld (SAW) fusion lines is discussed. During large-scale pipe tests with flaws in the center of the SAW, the crack tended to grow into the fusion line. The fracture toughness of the base metal, the SAW, and the fusion line were determined and compared. The major conclusion reached is that although the fusion line had a higher initiation toughness than the weld metal, the fusion-line J-R curve reached a steady-state value while the SAW J-R curve increased. Last, carbon steel fracture experiments containing circumferential flaws with periods of unstable crack jumps during steady ductile tearing are discussed. These instabilities are believed to be due to dynamic strain aging (DSA). The paper discusses DSA, a screening criteria developed to predict DSA, and the ability of the current J-based methodologies to assess the effect of these crack instabilities. The effect of loading rate on the strength and toughness of several different carbon steel pipes at LWR temperatures is also discussed.

  15. Transition Metal Complexes of Phosphinous Acids Featuring a Quasichelating Unit: Synthesis, Characterization, and Hetero-bimetallic Complexes.

    PubMed

    Allefeld, Nadine; Bader, Julia; Neumann, Beate; Stammler, Hans-Georg; Ignat'ev, Nikolai; Hoge, Berthold

    2015-08-17

    Diorganophosphane oxides were employed as preligands for the synthesis of catalytically active transition metal complexes of the phosphinous acids (CF3)2POH and (C2F5)2POH. Their reactions with solid PtCl2 and PdCl2 led to the formation of mononuclear phosphinous acid complexes [Cl2M{P(R(f))2OH}2] (M = Pd, Pt; R(f) = C2F5, CF3), which can be crystallized, for example, as its pyridinium salts, 2[HPy](+)[Cl2Pd{P(CF3)2O}2](2-). In vacuo HCl is liberated from the neutral palladium complexes affording mixtures of di- and polynuclear complexes. Moreover, (C2F5)2POH was reacted with several β-diketonato complexes of palladium, platinum, and nickel yielding air- and moisture-stable complexes [(acac)M{[P(R(f))2O]2H}], featuring a quasichelating phosphinous acid phosphinito unit {P(R(f))2O···H···O(R(f))2P}(-). Treatment of [Ni(Cp)2] (Cp = cyclopentadienyl) and [(cod)RhCl]2 (cod = 1,5-cyclooctadiene) with (C2F5)2POH leads to the substitution of one Cp or chloro ligand by a quasichelating unit. The novel coordination compounds were characterized by NMR and IR spectroscopies, mass spectrometry, and X-ray diffraction analysis. The platinum complex [(acac)Pt{[P(C2F5)2O]2H}] (acac = acetylacetonato) was used for the construction of hetero-bimetallic complexes by the treatment with [(cod)RhCl]2 and [Ni(Cp)2]. The trinuclear bimetallic complex [{(acac)Pt[P(C2F5)2O]2}2Ni] is the first structurally characterized hetero-bimetallic species containing a bis(perfluoroalkyl)phosphinito bridge.

  16. Synthesis of Pt-Pd bimetallic nanoparticles anchored on graphene for highly active methanol electro-oxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Yuting; Chang, Gang; Shu, Honghui; Oyama, Munetaka; Liu, Xiong; He, Yunbin

    2014-09-01

    A simple, one-step reduction route was employed to synthesize bimetallic Pt-Pd nanoparticles (Pt-PdNPs) supported on graphene (G) sheets, in which the reduction of graphite oxide and metal precursor was carried out simultaneously using ascorbic acid as a soft reductant. The morphology and structure of Pt-PdNPs/G composites were characterized using X-ray diffraction, Transmission Electron Microscopy, Field Emission Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analysis. The results show that Pt-Pd bimetallic nanoparticles were successfully synthesized and evenly anchored on the graphene sheets. Electrochemical experiments, including cyclic voltammetry and chronoamperometric measurements, were performed to investigate the electrochemical and electrocatalytic properties of the Pt-PdNPs/G composites. It was found that Pt-PdNPs/G composites show better electrocatalytic activity and stability towards the electro-oxidation of methanol than its counterparts such as composites composed of graphene-supported monometallic nanoparticles (PtNPs/G, PdNPs/G) and free-standing (Pt-PdNPs) and Vulcan-supported bimetallic Pt-Pd nanoparticles (Pt-PdNPs/V). The results could be attributed to the synergetic effects of the Pt-Pd nanoparticles and the enhanced electron transfer of graphene. The electrocatalytic activity of Pt-PdNPs/G changed with the Pd content in the Pt-Pd alloy, and the best performance was achieved with a Pt-Pd ratio of 1/3 in an alkaline environment. Our study indicates the potential use of Pt-PdNPs/G as new anode catalyst materials for direct methanol fuel cells.

  17. Near-Monodisperse Ni-Cu Bimetallic Nanocrystals of Variable Composition: Controlled Synthesis and Catalytic Activity for H2 Generation

    SciTech Connect

    Zhang, Yawen; Huang, Wenyu; Habas, Susan E.; Kuhn, John N.; Grass, Michael E.; Yamada, Yusuke; Yang, Peidong; Somorjai, Gabor A.

    2008-07-22

    Near-monodisperse Ni{sub 1-x}Cu{sub x} (x = 0.2-0.8) bimetallic nanocrystals were synthesized by a one-pot thermolysis approach in oleylamine/1-octadecene, using metal acetylacetonates as precursors. The nanocrystals form large-area 2D superlattices, and display a catalytic synergistic effect in the hydrolysis of NaBH{sub 4} to generate H{sub 2} at x = 0.5 in a strongly basic medium. The Ni{sub 0.5}Cu{sub 0.5} nanocrystals show the lowest activation energy, and also exhibit the highest H{sub 2} generation rate at 298 K.

  18. Facile Synthesis of Porous Dendritic Bimetallic Platinum-Nickel Nanocrystals as Efficient Catalysts for the Oxygen Reduction Reaction.

    PubMed

    Eid, Kamel; Wang, Hongjing; Malgras, Victor; Alothman, Zeid Abdullah; Yamauchi, Yusuke; Wang, Liang

    2016-05-01

    Certain bimetallic nanocrystals (NCs) possess promising catalytic properties for electrochemical energy conversion. Herein, we report a facile method for the one-step synthesis of porous dendritic PtNi NCs in aqueous solution at room temperature that contrasts with the traditional multistep thermal decomposition approach. The dendritic PtNi NCs assembled by interconnected arms are efficient catalysts for the oxygen reduction reaction. This direct and efficient method is favorable for the up-scaled synthesis of active catalysts used in electrochemical applications. PMID:26879517

  19. Direct hydrogenation of biomass-derived butyric acid to n-butanol over a ruthenium-tin bimetallic catalyst.

    PubMed

    Lee, Jong-Min; Upare, Pravin P; Chang, Jong-San; Hwang, Young Kyu; Lee, Jeong Ho; Hwang, Dong Won; Hong, Do-Young; Lee, Seung Hwan; Jeong, Myung-Geun; Kim, Young Dok; Kwon, Young-Uk

    2014-11-01

    Catalytic hydrogenation of organic carboxylic acids and their esters, for example, cellulosic ethanol from fermentation of acetic acid and hydrogenation of ethyl acetate is a promising possibility for future biorefinery concepts. A hybrid conversion process based on selective hydrogenation of butyric acid combined with fermentation of glucose has been developed for producing biobutanol. ZnO-supported Ru-Sn bimetallic catalysts exhibits unprecedentedly superior performance in the vapor-phase hydrogenation of biomass-derived butyric acid to n-butanol (>98% yield) for 3500 h without deactivation. PMID:25123894

  20. Catalytic activity of bimetallic catalysts highly sensitive to the atomic composition and phase structure at the nanoscale.

    PubMed

    Shan, Shiyao; Petkov, Valeri; Prasai, Binay; Wu, Jinfang; Joseph, Pharrah; Skeete, Zakiya; Kim, Eunjoo; Mott, Derrick; Malis, Oana; Luo, Jin; Zhong, Chuan-Jian

    2015-12-01

    The ability to determine the atomic arrangement in nanoalloy catalysts and reveal the detailed structural features responsible for the catalytically active sites is essential for understanding the correlation between the atomic structure and catalytic properties, enabling the preparation of efficient nanoalloy catalysts by design. Herein we describe a study of CO oxidation over PdCu nanoalloy catalysts focusing on gaining insights into the correlation between the atomic structures and catalytic activity of nanoalloys. PdCu nanoalloys of different bimetallic compositions are synthesized as a model system and are activated by a controlled thermochemical treatment for assessing their catalytic activity. The results show that the catalytic synergy of Pd and Cu species evolves with both the bimetallic nanoalloy composition and temperature of the thermochemical treatment reaching a maximum at a Pd : Cu ratio close to 50 : 50. The nanoalloys are characterized structurally by ex situ and in situ synchrotron X-ray diffraction, including atomic pair distribution function analysis. The structural data show that, depending on the bimetallic composition and treatment temperature, PdCu nanoalloys adopt two different structure types. One features a chemically ordered, body centered cubic (B2) type alloy consisting of two interpenetrating simple cubic lattices, each occupied with Pd or Cu species alone, and the other structure type features a chemically disordered, face-centered cubic (fcc) type of alloy wherein Pd and Cu species are intermixed at random. The catalytic activity for CO oxidation is strongly influenced by the structural features. In particular, it is revealed that the prevalence of chemical disorder in nanoalloys with a Pd : Cu ratio close to 50 : 50 makes them superior catalysts for CO oxidation in comparison with the same nanoalloys of other bimetallic compositions. However, the catalytic synergy can be diminished if the Pd50Cu50 nanoalloys undergo

  1. Ferritin-mediated biomimetic synthesis of bimetallic Au-Ag nanoparticles on graphene nanosheets for electrochemical detection of hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Wang, Li; Wang, Jiku; Ni, Pengjuan; Li, Zhuang

    2015-03-01

    We demonstrated a biomimetic green synthesis of bimetallic Au-Ag nanoparticles (NPs) on graphene nanosheets (GNs). The spherical protein, ferritin (Fr), was bound onto GNs and served as the template for the synthesis of GN/Au-Ag nanohybrids. The created GN/Au-Ag nanohybrids were further utilized to fabricate a non-enzymatic amperometric biosensor for the sensitive detection of hydrogen peroxide (H2O2), and this biosensor displayed high performances to determine H2O2 with a detection limit of 20.0 × 10-6 M and a linear detection range from 2.0 μM to 7.0 mM.

  2. Direct hydrogenation of biomass-derived butyric acid to n-butanol over a ruthenium-tin bimetallic catalyst.

    PubMed

    Lee, Jong-Min; Upare, Pravin P; Chang, Jong-San; Hwang, Young Kyu; Lee, Jeong Ho; Hwang, Dong Won; Hong, Do-Young; Lee, Seung Hwan; Jeong, Myung-Geun; Kim, Young Dok; Kwon, Young-Uk

    2014-11-01

    Catalytic hydrogenation of organic carboxylic acids and their esters, for example, cellulosic ethanol from fermentation of acetic acid and hydrogenation of ethyl acetate is a promising possibility for future biorefinery concepts. A hybrid conversion process based on selective hydrogenation of butyric acid combined with fermentation of glucose has been developed for producing biobutanol. ZnO-supported Ru-Sn bimetallic catalysts exhibits unprecedentedly superior performance in the vapor-phase hydrogenation of biomass-derived butyric acid to n-butanol (>98% yield) for 3500 h without deactivation.

  3. Vertically aligned nanostructure scanning probe microscope tips

    DOEpatents

    Guillorn, Michael A.; Ilic, Bojan; Melechko, Anatoli V.; Merkulov, Vladimir I.; Lowndes, Douglas H.; Simpson, Michael L.

    2006-12-19

    Methods and apparatus are described for cantilever structures that include a vertically aligned nanostructure, especially vertically aligned carbon nanofiber scanning probe microscope tips. An apparatus includes a cantilever structure including a substrate including a cantilever body, that optionally includes a doped layer, and a vertically aligned nanostructure coupled to the cantilever body.

  4. Metal oxide nanostructures with hierarchical morphology

    DOEpatents

    Ren, Zhifeng; Lao, Jing Yu; Banerjee, Debasish

    2007-11-13

    The present invention relates generally to metal oxide materials with varied symmetrical nanostructure morphologies. In particular, the present invention provides metal oxide materials comprising one or more metallic oxides with three-dimensionally ordered nanostructural morphologies, including hierarchical morphologies. The present invention also provides methods for producing such metal oxide materials.

  5. Processing of Nanostructured Devices Using Microfabrication Techniques

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W (Inventor); Xu, Jennifer C (Inventor); Evans, Laura J (Inventor); Kulis, Michael H (Inventor); Berger, Gordon M (Inventor); Vander Wal, Randall L (Inventor)

    2014-01-01

    Systems and methods that incorporate nanostructures into microdevices are discussed herein. These systems and methods can allow for standard microfabrication techniques to be extended to the field of nanotechnology. Sensors incorporating nanostructures can be fabricated as described herein, and can be used to reliably detect a range of gases with high response.

  6. Co-sputter deposited nickel-copper bimetallic nanoalloy embedded carbon films for electrocatalytic biomarker detection

    NASA Astrophysics Data System (ADS)

    Shiba, Shunsuke; Kato, Dai; Kamata, Tomoyuki; Niwa, Osamu

    2016-06-01

    We report the fabrication of a nickel (Ni)-copper (Cu) bimetallic nanoalloy (~3 nm) embedded carbon film electrode with the unbalanced magnetron (UBM) co-sputtering technique, which requires only a one-step process at room temperature. Most of each nanoalloy body was firmly embedded in a chemically stable carbon matrix with an atomically flat surface (Ra: 0.21 nm), suppressing the aggregation and/or detachment of the nanoalloy from the electrode surface. The nanoalloy size and composition can be controlled simply by individually controlling the target powers of carbon, Ni and Cu, which also makes it possible to localize the nanoalloys near the electrode surface. This electrode exhibited excellent electrocatalytic activity for d-mannitol, which should be detected with a low detection limit in urine samples for the diagnosis of severe intestinal diseases. With a Ni/Cu ratio of around 64/36, the electrocatalytic current per metal area was 3.4 times larger than that of an alloy film electrode with a similar composition (~70/30). This improved electrocatalytic activity realized higher stability (n = 60, relative standard deviation (RSD): 4.6%) than the alloy film (RSD: 32.2%) as demonstrated by continuous measurements of d-mannitol.We report the fabrication of a nickel (Ni)-copper (Cu) bimetallic nanoalloy (~3 nm) embedded carbon film electrode with the unbalanced magnetron (UBM) co-sputtering technique, which requires only a one-step process at room temperature. Most of each nanoalloy body was firmly embedded in a chemically stable carbon matrix with an atomically flat surface (Ra: 0.21 nm), suppressing the aggregation and/or detachment of the nanoalloy from the electrode surface. The nanoalloy size and composition can be controlled simply by individually controlling the target powers of carbon, Ni and Cu, which also makes it possible to localize the nanoalloys near the electrode surface. This electrode exhibited excellent electrocatalytic activity for d

  7. Dehalogenation of Polybrominated Diphenyl Ethers and Polychlorinated Biphenyl by Bimetallic, Impregnated, and Nanoscale Zerovalent Iron

    PubMed Central

    Zhuang, Yuan; Ahn, Sungwoo; Seyfferth, Angelia L.; Masue-Slowey, Yoko; Fendorf, Scott; Luthy, Richard G.

    2011-01-01

    Nanoscale zerovalent iron particles (nZVI), bimetallic nanoparticles (nZVI/Pd), and nZVI/Pd impregnated activated carbon (nZVI/Pd-AC) composite particles were synthesized and investigated for their effectiveness to remove polybrominated diphenyl ethers (PBDEs) and/or polychlorinated biphenyls (PCBs). Palladization of nZVI promoted the dehalogenation kinetics for mono- to tri-BDEs and 2,3,4-trichlorobiphenyl (PCB 21). Compared to nZVI, the iron-normalized rate constants for nZVI/Pd were about 2-, 3-, and 4-orders of magnitude greater for tri-, di-, and mono-BDEs, respectively, with diphenyl ether as a main reaction product. The reaction kinetics and pathways suggest an H-atom transfer mechanism. The reaction pathways with nZVI/Pd favor preferential removal of para-halogens on PBDEs and PCBs. X-ray fluorescence mapping of nZVI/Pd-AC showed that Pd mainly deposits on the outer part of particles, while Fe was present throughout the activated carbon particles. While BDE 21 was sorbed onto activated carbon composites quickly, debromination was slower compared to reaction with freely dispersed nZVI/Pd. Our XPS and chemical data suggest about 7% of the total iron within the activated carbon was zero-valent, which shows the difficulty with in-situ synthesis of a significant fraction of zero-valent iron in the micro-porous material. Related factors that likely hinder the reaction with nZVI/Pd-AC are the heterogenous distribution of nZVI and Pd on activated carbon and/or immobilization of hydrophobic organic contaminants at the adsorption sites thereby inhibiting contact with nZVI. PMID:21557574

  8. Titania-supported bimetallic catalysts combined with HZSM-5 for Fischer-Tropsch synthesis

    SciTech Connect

    Jothimurugesan, K.; Gangwal, S.K.

    1998-04-01

    The Fischer-Tropsch synthesis (FTS) can convert coal or natural gas derived synthesis gas (CO + H{sub 2}) to liquid fuels and high-value chemicals. Fischer-Tropsch synthesis was studied in a fixed-bed reactor over single-metal and bimetallic alloy catalysts, selected from Co, Ni, and Fe, supported on TiO{sub 2} at a total metal loading of 10 wt%. The catalysts, prepared by incipient wetness impregnation using nitrate precursors, were tested as is and in combination with a HZSM-5 zeolite. The test conditions were 1 MPa, 250 C, H{sub 2}/CO = 1, and weight hourly space velocity (WHSV) = 0.77 h{sup {minus}1}. Alloying of metals resulted in a significant enhancement in CO conversion without an increase in methane selectivity. A 50:50 weight ratio Co-Ni catalyst physically mixed with HZSM-5 (5% Co-5% Ni/TiO{sub 2} + HZSM-5) gave the highest CO conversion (45.2%) at the conditions tested. This compares to conversion of 8.9% and 10.5% with Co-only and Ni-only catalysts, respectively. Mixing the Co-Ni catalyst with HZSM-5 resulted in a significant reduction in methane selectivity and a significant increase in C{sub 4}{sup +} selectivity. The aromatic fraction increased from 1.5 to 8.1 wt%, the C{sub 2}{sup +} olefins were nearly eliminated, and i-C{sub 4}H{sub 10} increased from 2.3 to 58.5 wt % in the C{sub 4} fraction.

  9. Pressure response of three-dimensional cyanide-bridged bimetallic magnets.

    PubMed

    Ohba, Masaaki; Kaneko, Wakako; Kitagawa, Susumu; Maeda, Takuho; Mito, Masaki

    2008-04-01

    Effects of pressure on the structures and magnetic properties of three types of 3-D cyanide-bridged bimetallic coordination polymer magnets, MnIICrIII ferrimagnet [Mn(en)]3[Cr(CN)6]2.4H2O (1; en = ethylenediamine), NiIICrIII ferromagnet [Ni(dipn)]3[Cr(CN)6]2.3H2O (2; dipn = N,N-di(3-aminopropyl)amine), and NiIIFeIII ferromagnet [Ni(dipn)]2[Ni(dipn)(H2O)][Fe(CN)6]2.11H2O (3), were systematically examined under hydrostatic pressure up to 19.8 GPa using a piston-cylinder-type pressure cell and a diamond anvil cell. The ferrimagnet 1 showed the reversible crystalline-to-amorphous-like phase change, and the magnetic phase transition temperature (TC) was reversibly changed from 69 K at 0 GPa to 126 K at 4.7 GPa. At higher pressure, the net magnetization was suppressed with increasing pressure, and the magnetic state at 19.8 GPa was assumed to be paramagnetic. The initial ferrimagnetic phase of 1 was not recovered after releasing the pressure from 19.8 GPa. The magnetic phase of 2 was reversibly converted between ferromagnetic and paramagnetic-like phase in the range 0

  10. Nanostructures, systems, and methods for photocatalysis

    SciTech Connect

    Reece, Steven Y.; Jarvi, Thomas D.

    2015-12-08

    The present invention generally relates to nanostructures and compositions comprising nanostructures, methods of making and using the nanostructures, and related systems. In some embodiments, a nanostructure comprises a first region and a second region, wherein a first photocatalytic reaction (e.g., an oxidation reaction) can be carried out at the first region and a second photocatalytic reaction (e.g., a reduction reaction) can be carried out at the second region. In some cases, the first photocatalytic reaction is the formation of oxygen gas from water and the second photocatalytic reaction is the formation of hydrogen gas from water. In some embodiments, a nanostructure comprises at least one semiconductor material, and, in some cases, at least one catalytic material and/or at least one photosensitizing agent.

  11. Microwave properties of ferromagnetic nanostructures.

    PubMed

    Valenzuela, R; Alvarez, G; Mata-Zamora, M E

    2008-06-01

    A review of the dynamic properties of nanostructured ferromagnetic materials at microwave frequencies (1-40 GHz) is presented. Since some confusion has recently appeared between giant magnetoimpedance (GMI) and ferromagnetic resonance (FMR), a detailed analysis is made in order to establish their differences. A brief review of a novel microwave absorption mode, the low-field microwave absorption (LFA) is then presented, together with a discussion about its similarities with GMI. Recent results on high-frequency measurements on nanogranular thin films and FMR in nanowire arrays are finally addressed.

  12. Dispersion and separation of nanostructured carbon in organic solvents

    NASA Technical Reports Server (NTRS)

    Landi, Brian J. (Inventor); Raffaelle, Ryne P. (Inventor); Ruf, Herbert J. (Inventor); Evans, Christopher M. (Inventor)

    2011-01-01

    The present invention relates to dispersions of nanostructured carbon in organic solvents containing alkyl amide compounds and/or diamide compounds. The invention also relates to methods of dispersing nanostructured carbon in organic solvents and methods of mobilizing nanostructured carbon. Also disclosed are methods of determining the purity of nanostructured carbon.

  13. Preparation and characterization of bi-metallic nanoparticle catalyst having better anti-coking properties using reverse micelle technique

    NASA Astrophysics Data System (ADS)

    Zacharia, Thomas

    Energy needs are rising on an exponential basis. The mammoth energy sources like coal, natural gas and petroleum are the cause of pollution. The large outcry for an alternate energy source which is environmentally friendly and energy efficient is heard during the past few years. This is where “Clean-Fuel” like hydrogen gained its ground. Hydrogen is mainly produced by steam methane reforming (SMR). An alternate sustainable process which can reduce the cost as well as eliminate the waste products is Tri-reforming. In both these reforming processes nickel is used as catalyst. However as the process goes on the catalyst gets deactivated due to coking on the catalytic surface. This goal of this thesis work was to develop a bi-metallic catalyst which has better anti-coking properties compared to the conventional nickel catalyst. Tin was used to dope nickel. It was found that Ni3Sn complex around a core of Ni is coking resistant compared to pure nickel catalyst. Reverse micelle synthesis of catalyst preparation was used to control the size and shape of catalytic particles. These studies will benefit researches on hydrogen production and catalyst manufactures who work on different bi-metallic combinations.

  14. In situ biosynthesis of Ag, Au and bimetallic nanoparticles using Piper pedicellatum C.DC: green chemistry approach.

    PubMed

    Tamuly, Chandan; Hazarika, Moushumi; Borah, Sarat Ch; Das, Manash R; Boruah, Manas P

    2013-02-01

    The synthesis of Ag, Au and Ag-Au bimetallic nanoparticles using Piper pedicellatum C.DC leaf extract is demonstrated here. The rapid formation of stable Ag and Au nanoparticles has been found using P. pedicellatum C.DC leaf extract in aqueous medium at normal atmospheric condition. Competitive reduction of Ag(+) and Au(3+) ions present simultaneously in solution during exposure to P. pedicellatum C.DC leaf extract leads to the synthesis of bimetallic Ag-Au nanoparticles in solution. Transmission electron microscopy (TEM) analysis revealed that the Ag nanoparticles predominantly form spherical in shape with the size range of 2.0±0.5-30.0±1.2 nm. In case of Au nanoparticles, the particles are spherical in shape along with few triangular, hexagonal and pentagonal shaped nanoparticles also observed. X-ray diffraction (XRD) studies revealed that the nanoparticles were face centered cubic (fcc) in shape. Fourier transform infrared spectroscopy (FTIR) showed nanoparticles were capped with plant compounds. The chemical constituents, viz. catechin, gallic acid, courmaric acid and protocatechuic acid of the leaf extract were identified which may act as a reducing, stabilizing and capping agent. The expected reaction mechanism in the formation of Ag and Au nanoparticles is also reported. PMID:23107941

  15. Mono/bimetallic water-stable lanthanide coordination polymers as luminescent probes for detecting cations, anions and organic solvent molecules.

    PubMed

    Wang, Huarui; Qin, Jianhua; Huang, Chao; Han, Yanbing; Xu, Wenjuan; Hou, Hongwei

    2016-08-01

    Eleven water-stable isostructural mono/bimetallic lanthanide coordination polymers (Ln-CPs) {[EuxTb1-x (HL)(H2O)3]·H2O}n (x = 1.0 (1), 0.9 (3), 0.8 (4), 0.7 (5), 0.6 (6), 0.4 (7), 0.3 (8), 0.2 (9), 0.1 (10), 0.05 (11), 0 (2), H4L = 5,5'-(1H-2,3,5-triazole-1,4-diyl)diisophthalic acid) with uncoordinated Lewis basic triazole sites within the pores were prepared. The Ln-CPs represented by 1 showed a rapid and drastic emission quenching induced by external Fe(3+) and Cr(3+) cations and CrO4(2-) and CO3(2-) anions in aqueous solution. In addition, because of the comparable emission intensities of Eu(3+) and Tb(3+) ions, bimetallic CP 8 can be used as a ratiometric luminescent sensor for organic solvent molecules. Moreover, the luminescent color of the 8 sensor in pyridine and in other guest solvents undergoes obvious changes that can be clearly distinguished by the naked eye. PMID:27443408

  16. Highly efficient removal of chromium(VI) by Fe/Ni bimetallic nanoparticles in an ultrasound-assisted system.

    PubMed

    Zhou, Xiaobin; Jing, Guohua; Lv, Bihong; Zhou, Zuoming; Zhu, Runliang

    2016-10-01

    Highly active Fe/Ni bimetallic nanocomposites were prepared by using the liquid-phase reduction method, and they were proven to be effective for Cr(VI) removal coupled with US irradiation. The US-assisted Fe/Ni bimetallic system could maintain a good performance for Cr(VI) removal at a wide pH range of 3-9. Based on the characterization of the Fe/Ni nanoparticles before and after reaction, the high efficiency of the mixed system could attribute to the synergistic effects of the catalysis of Ni(0) and US cavitation. Ni(0) could facilitate the Cr(VI) reduction through electron transfer and catalytic hydrogenation. Meanwhile, US could fluidize the Fe/Ni nanoparticles to increase the actual reactive surface area and clean off the co-precipitated Fe(III)-Cr(III) hydroxides to maintain the active sites on the surface of the Fe/Ni nanoparticles. Thus, compared with shaking, the US-assisted Fe/Ni system was more efficient on Cr(VI) removal, which achieved 94.7% removal efficiency of Cr(VI) within 10 min. The pseudo-first-order rate constant (kobs) in US-assisted Fe/Ni system (0.5075 min(-1)) was over 5 times higher than that under shaking (0.0972 min(-1)). Moreover, the Fe/Ni nanoparticles still have a good performance under US irradiation after 26 days aging as well as regeneration. PMID:27393969

  17. Pt-Co Bimetallic Catalyst Supported on Single Walled Carbon Nanotube: XAS and Aqueous Phase Reforming Activity Studies

    SciTech Connect

    Wang, X.; Li, N; Pfefferle, L; Haller, G

    2009-01-01

    We have developed a simple method to create a catalyst with atomically dispersed Pt on top of Co nanoparticles on single walled carbon nanotubes (SWNT) supports by sequential impregnation of Pt(II) and Co(II) solutions following by hydrogen reduction. The aqueous phase reforming activity is much higher than for Pt monometallic catalysts on SWNT supports prepared by several methods, either pre-reduced in hydrogen or in the liquid phase. The high selectivity of the monometallic catalysts is maintained for the bimetallic systems. The Extended X-ray Absorption Fine Structure (EXAFS) results at the Pt LIII edge show no observable Pt-Pt bond. Only Pt-Co bonds were observed, indicating high dispersion of Pt. The enhanced activity comes from two sources: the high dispersion of Pt and the effect of the Co as co-catalyst or modifier. This contribution demonstrates the possibility to further engineer bimetallic catalysts to improve the aqueous phase reforming activity, especially to retain good selectivity at high conversion.

  18. Highly stable bimetallic AuIr/TiO2 catalyst: physical origin of the intrinsic stability against sintering

    NASA Astrophysics Data System (ADS)

    Marinero, Ernesto; Han, Chan Wan; Majundar, Paulami; Aguilar-Tapia, Antonio; Zanella, Rodolfo; Greeley, Jeffrey; Otarlan, Volkan

    It has been a long-lived research topic in the field of heterogeneous catalysis to find a way to stabilizing supported Au catalysts against sintering. Herein, we report highly stable AuIr bimetallic nanoparticles on TiO2 synthesized by sequential deposition-precipitation. To understand the physical origin of the high stability AuIr/TiO2 system, we have used scanning transmission electron microscopy (STEM), STEM-tomography and density functional theory (DFT) calculations. 3D structures of AuIr/TiO2 obtained by STEM-tomography indicate that AuIr nanoparticles on TiO2 have intrinsically lower free energy and less driving force for sintering than Au nanoparticles. DFT calculations on segregation behavior of AuIr slabs on TiO2 showed that the presence of Ir near the TiO2 surface increases the adhesion energy of the bimetallic slabs to the TiO2 and the attractive interactions between Ir and TiO2 lead to higher stability of the AuIr nanoparticles compared to Au nanoparticles.

  19. Enhanced bioremediation of heavy metal from effluent by sulfate-reducing bacteria with copper-iron bimetallic particles support.

    PubMed

    Zhou, Qin; Chen, Yongzhe; Yang, Ming; Li, Wenkai; Deng, Le

    2013-05-01

    The purpose of this study was to investigate the potential of copper-iron bimetallic particles supported sulfate-reducing bacteria (SRB) in enhancing the reduction of Cu(2+) and Zn(2+) in effluent. The results showed that the copper-iron bimetallic particles can enhance Cu(2+) and Zn(2+) removal and the resistance of the sulfate-reducing bacteria towards metals toxicity, the inhibiting concentration of Cu(2+) and Zn(2+) for SRB was significantly increased (from 100 to 200 mg/L for Cu(2+) and 300 to 400 mg/L for Zn(2+)). The removal efficiencies of Cu(2+) and Zn(2+) (initial concentration 100 mg/L) were 98.17% and 99.67% in SRB-Cu/Fe system after 48 h, while only 29.83% Cu(2+), 90.88% Zn(2+) and 63.81% Cu(2+), 72.63% Zn(2+) were removed in the SRB and Cu/Fe system at the same condition.

  20. Real-time feedback system for controlling the optical density of bimetallic thin-film grayscale photomasks

    NASA Astrophysics Data System (ADS)

    Dykes, James Methven

    Bimetallic grayscale photomasks consist of a bi-layer thin-film that is converted into a transparent oxide upon laser exposure. The film's transparency is a function of the laser power allowing grayscale masks to be produced by controlling the laser's intensity during the mask-writing process. The mask's accuracy is determined by the control over the laser power. Using a direct-write raster-scanning system, a feedback-controlled design is created through the addition of photodiode sensors and an FPGA-based microprocessor subsystem allowing measurements of the mask's transparency to control the laser's power. When patterning mask lines ranging from 1.7 to 0.5 OD on a 100 nm Bi/In film using an 8-bit grayscale without OD feedback, the lines produced are accurate to 0.02 OD for exposures <50 mW. Using OD feedback, the accuracy improves to 0.002 OD on the same range. A model for predicting the OD profile of bimetallic grayscale mask lines is also presented.